For sure max depth should be greater than depth per pass. It does not have to be a multiple, the CAD tool with make a thinner last pass to reach the exact final/max depth.
For surfacing a (MDF) wasteboard, and unless it’s completely bent/crooked, I would use 0.04" per pass or less, program 3 passes (e.g. max depth 0.12"), run it, pause it after the first pass and inspect whether the endmill has reached everywhere, if so stop the job there, if not let the second pass run, pause again and check, and if there really are spots that have not been touched, let the third pass run. That would be surprising, 0.1" is a LOT of material to be removing to flatten a wasteboard.
You want to make sure all spots have been surfaced, but at the same time minimize the amount of material you are shaving off (because you’ll want to re-surface later, and then you’ll be happy you did not take too much away the previous time)