Hybrid BSO incorrect calculation result in business rule

Summary:

I'm going in circles here, so figured I'd ask the community for some help. I have a pretty small cube, so am able to have full dynamic calc on sparse dimension parents and dense members in a Hybrid BSO cube. I've written a calculation in a business rule that is calculating a statistical account based on adding and subtracting values from parent account and other sparse dimension members and I get an answer that is close but not exact vs. pulling the data in smartview and doing an Excel formula. This calculation requires bringing together data from a