SSc5.1 - Please explain "whichever is greater"

You have to run both calculations to see what each requires for minimum vegetated area. Then, your project is held to providing whichever of those minimum vegetated amounts is larger. So (extrapolating a bit from your numbers) - It appears that your Total Site Area (including Bldg Footprint) is 45,185 SF and your Bldg Footprint is 17,775 SF: -- Calc A (50% Of Total Site without Bldg Foot) -> 45,185 SF Total Site - 17,775 SF Bldg Foot = 27,410 SF Non-Bldg Site -> 27,410 SF Non-Bldg Site x 50% = 13,705 SF Required -- Calc B (20% of Total Site with Bldg Foot) -> 45,185 SF Total Site x 20% = 9,037 SF Required Project-specific Requirements: Must provide at least 13,705 SF (Calc A method) as that is the larger of the two calculated minimums. It's not always one verses the other as it depends heavily on how much of your site is occupied by the building. In cases where the building footprint comprises most of the total site area, then Calc B is larger. Conversely in cases where the building footprint is only a small portion of the total site area, then Calc A is larger.