Why two numbers
A plan that uses every millimetre looks good on paper but can be hard to load. When the geometric count and the count with clearance match, the layout has room to spare. When they differ, the last pallet only goes in if the loader is precise and the dimensions are exactly as published.
Example
In the 13.6 m European trailer from DP World's spec, our engine fits 34 EPAL 1 pallets geometrically and 33 with clearance. The 34th pallet fits only if every pallet goes in exactly where the plan puts it.
The allowance is ours
100 mm and 50 mm are our assumptions, not a standard. Real pallets bulge, overhanging goods take space, and loaders differ. The load planner lets you set your own dimensions.