This code runs at the start of the print. If the plate type selected when slicing is the textured PEI plate, it sets the Z offset of the probe .04 mm lower to “squish” the filament a bit more on the first layer. If the plate type is “High Temp Plate” (which is what one uses with the Wham Bam PEX plate), the Z offset of the probe is raised .03mm for less squish, as it’s a smooth plate that doesn’t need as much squish.
See also Bambu Lab Modified Start and End gcode by thrutheframe | Download free STL model | Printables.com