Gross up entities on the reporting tree

Hello,

I am running management reporter 2012 and I am trying to gross up my entities. I see the option on the reporting tree column K as "rollup %" but from what i tried it can only multiply the unit. How do i for example take 50% of the data and gross it up to 100% without needing to put in the business unit twice. We have some ownership as 67% or 80%.

thanks