Growth margin
Consumables, new clothing and seasonal items need temporary space.
Handling margin
Shelves are easier to use when they are not compressed.
Sorting margin
An empty shelf or bin helps during category review.
Fullness is feedback
Persistent 100% fullness can mean the assigned category exceeds the available space.
Practical boundary. Measure first, respect product load limits, and do not improvise wall, ceiling or overhead installations when the structure or appropriate hardware is uncertain.