1/ This passage from the Manafort Sentencing Memo is weird. Look it over and try to understand the relationship between Firm A and Entity B. Notice that "Entity B" is not a firm (LLC, corporation, etc.). 
2/ Firm A works for Entity B. Entity B makes payments to Firm A, and Firm A earns a 6% commission on those payments. (I don't get it. A performs work for B. A "makes expenditures" to B. B earns a commission on those expenditures.)
3/ What kind of business arrangement is this? At first, I thought Firm A was a fundraiser for Entity B (a charity or foundation of some sort), and A earned a 6% commission on funds raised. But that doesn't fit. A earns a 6% commission "on expenditures made to it by B".
4/ Of course, this could simply be the result of rather unartful construction by Mueller's office in an attempt to hide the identities of Firm A and Entity B.
