Do you remember the very long dispute we had regarding refueling a 787 for FSX that didn't work. Refueling completed too early. I had to send you an amimation before you finally believed me. You checked the code and found out that the amount of fuel had changed and so GSX didn't work.
This is completely irrelevant in this case, because in that case it was the QW787, which is flagged in FSX/P3D to NOT be refueled by GSX.
In that case, the refueling procedure is completely different, since GSX is monitoring the airplane refueling itself and it goes away if the fuel quantity stop increasing in a given amount of time or even it decreases so yes, in THAT case, GSX COULD have been confused by the APU consumption.
This case is completely different, the Aerosoft CRJ is flagged to be refueled BY GSX, so nothing of the above applies: GSX just fill the fuel quantity you asked for, it's not trying to read constantly if the airplane is filling, like in the other case.
If the difference is just the APU consumption, why this should be a problem ? If you asked for a certain quantity, you will be given that quantity, if you are burning fuel in the meantime, it's your responsibility to ask for extra fuel, if your goal was to end up with a precise quantity on tanks just before starting the engine.
As I've said, I have tried it already, using your same numbers, which roughly means asking for 70%, when you had 15%. At the end of the refuel process, I had 68%, which really looks like the fuel consumed by the APU during that time, clearly indicating that even if the APU is running, you are being given the quantity you are asked for.