That way you're not fooling yourself with over ambitious hp #'s at the flywheel. To be honest, if I used 30%, I'd feel like a w*anker.
99.6kW @ wheels is 177hp (and feels like it - vs std 86kw) 111kw @ wheels is 197hp (and feels like it) - vs std 86kw)
I'm happy with the conversion, but what really matters is that the same dyno is used and the improvement from 99.6 to 111 is genuine. Maybe it's not EXACTLY 11.4kW, but it IS in the right direction. ie MORE POWER!