The amount of fuel returning to the sump is the flow rate from the pump
minus the amount the engine is burning.  So if the pump is putting out
35
gph, and the engine is burning 15 gph you've got 25 gph going back to
the
sump.

Oops; I'm embarrassed.  I'm not really so mathematically challenged that
I can't subtract.  Let's just call it a typo.   Let's see - 35 minus 15
is ah . . . ah . . well; I don't think it's 25.

Al