Ornis
Just a coincidence that the quantity of fuel drained is about the same as the unusable fuel quantity if the forward transfer pump is not replenishing the supply tanks at cruise attitude.
(..but it's even closer to the amount unusable at low speed attitude with an aft pump off!)
Ornis, it's unusable because the pump can't get at the fuel at that attitude. As the drain point is in the same location, how do you drain it? Are you saying they drained un-drainable fuel!