The bracket is bent one way for a wood counter and another way for stone. You decide with pliers, before the machine goes in.

Establish the countertop material before you bend anything

This is the decision the whole installation turns on, and it is made before the machine goes near the opening. Bosch’s rule is direct: side mount for marble, granite and other very hard materials that cannot easily be drilled, top mount for wood and materials that can. Both methods use the same brackets, seated by pushing their two small tabs into the two slots at the dishwasher’s front corners, and both start with bending along the small holes in the same direction as those tabs. What differs is where the screw ends up, and therefore how the perforated edge gets folded. Decide, then bend once. Sheet metal that has been bent, straightened and bent again is not the same part.

Measure the opening, because at exactly 23 5/8 inches the method changes

This is the specification almost nobody checks and it is in Bosch’s own note. If the opening measures more than 23 5/8 in, which is 600 mm, use the top or side mount methods. If it measures exactly 23 5/8 in, the alternate side mount applies, which uses a side mount force distributor in each side. Cabinet openings get cut to whatever the previous appliance needed, so an opening at exactly 600 mm is common in kitchens built around metric or European appliances. Take the measurement before you order the machine if you can, and certainly before you start folding brackets.

Level it before you fasten it, not after

The machine sits on adjustable feet and the sequence matters. Level side to side and front to back while it is still free to move, then fasten. Doing it the other way around means either working the feet against a machine that is already anchored, or loosening the brackets you just set and losing the position. Leveling is not cosmetic on a dishwasher: it affects how water sits in the tub and how the door lines up with the cabinet faces on either side, so a machine that drains oddly or has a door that looks crooked in the opening is frequently just a machine that was fastened before it was leveled.

Check that the brackets can actually reach before the machine goes all the way back

This is the practical failure that produces an installed dishwasher and no way to secure it. On side mount, the brackets have to land on the cabinet walls, and if the machine sits further back than the brackets were folded for, they meet nothing. On top mount, the gap between the top of the machine and the underside of the counter has to be small enough for the bracket to bridge, and on a thick stone slab with a subtop it may not be. Slide the machine most of the way in, check both, and pull it back out to adjust while that is still easy. Doing this after the water and drain are connected is a much worse afternoon.

There is a third way for stone, and it is worth knowing about

If side mount into the cabinets is awkward, and drilling stone is not something you want to attempt, there is a category of adhesive mounting bracket made specifically for this. It bonds to the underside of the stone and presents a threaded hole that accepts the machine screw, so the dishwasher is effectively top mounted without anything being drilled into the counter or the cabinets. It is a legitimate answer in a kitchen where the geometry does not suit side mount, and it is a great deal better than the two things people do instead, which are gluing a wooden batten under the counter or leaving the machine unfastened.

Never leave it unfastened, even temporarily

This is the outcome all of the above exists to prevent, and it is common because it is easy. A dishwasher that is plumbed, powered and running looks finished, and the mounting brackets are the last step and the least visible one. An unfastened machine moves when the door is opened with a loaded rack on it, which stresses the water and drain connections you just made, and in a household with small children a heavy door on an unanchored appliance is a real hazard. If the brackets cannot be made to work today, that is a reason to solve the mounting rather than a reason to run it for a few weeks and see.

Budget for the shutoff valve you are about to discover

The single most common reason a dishwasher swap runs long has nothing to do with the dishwasher. The shutoff valve under the sink has often not been turned in fifteen years, and old multi-turn valves that have sat open that long frequently will not close, or will not reseal afterward. Find and test that valve before the new machine is out of the box, while you still have the option of scheduling a plumber rather than needing one. The same applies to the supply line, which should generally be replaced rather than reused, and to the drain connection, where high loop and air gap requirements vary by jurisdiction and are worth checking locally rather than assuming.

Bosch says these instructions are for qualified installers

Worth reading literally rather than as boilerplate. The manual states the installation instructions are intended for use by qualified installers, and the reason is that a dishwasher installation touches three trades at once: a water supply, a drain, and a permanent electrical connection, in a confined space under a counter. A confident homeowner can absolutely do a like-for-like swap. A first-time installation where the supply, drain and circuit do not yet exist is a different job, and the parts of it that go wrong go wrong slowly and expensively behind a cabinet.