LEED Campus - Large Site Area

We are looking at submitting this for a LEED Campus submittal but have some questions about the calculations. We have an existing 10 million SF campus, 92% of which is "open space" (so well above the 30% requirement). However - a lot of that area is un-mowed / unirrigated turf or grass. Do we simply have to meet the minimum requirements (i.e. provide 25% of the original 30%) of vegetated open space, which would equate to about 800,000sf; OR do we have to provide 25% of the provided 92% which would equate to about 2.5 Million SF of vegetated open space? If it's the latter, it seems as if we're being penalized for having more open space than required. Any insight would be helpful, thanks!