Alternative path - maximum achievable points

Hello everyone! In order to reduce use of potable water, WCs will be served by rainwater collected on-site. We are attempting WE c3, following the alternative path that allows to use on-site alternative sources of water to achieve water use reduction, as described in Water Use Reduction Additional Guidance http://www.usgbc.org/Docs/Archive/General/Docs6493.pdf Based on calculations made, percentage of reduction of potable water use in all fixtures (flush and flow fixtures) is 96 %, higher than 40% (= 4 points). We are now filling the online form, and it seems that, by selecting Alternative Path Option, maximum points achievable are 2 (equal to a percentage reduction of 30%), even thou percentage of reduction is higher than 40%. Can anybody suggest us how to attempt to 4 point? or, in any case, by following Alternative path, are maximum achievable points equal to 2? Thanks in advance