Rookie paint question

Hey all.
I'm about to paint my engine bay hemi O, and I'm using SunCryl 327 paint.
Can someone knowledgeable please tell me in english what this means?
10-15% reduction with 181-184 Reducers. With hardener: 8 parts color to 1 part 325C000or 325C007 (optional). (8:1:10-15%)

I get the 8 parts color to 1 part (325C000 or 325C007) hardener.
but when they say 10-15% reduction, do I need to look at the total mass in the mixing cup, calculate 15% and add that much reducer?

Thanks,
Stu