Billing units for j1040

We are being denied by Medicare/novitas for exceeding maximum allowable units billed for j1040 (80mg methylprednisolone)...This is always when billed at 8 units...The biller says she is going by the report...I havent actually looked into this, but if I understand correctly the max alowable for this code is 3 units...
i am assuming I need to read the report to determine the dosage and bring it bring to the billers attention...

I would think that any portion of an 80 mg bottle used would represent 1 unit and knowing the allowable is 3 units, no matter how much more than 240 mg is injected, we can only bill for 3?
i am not a clinician, just thinking logically...

thanks for your responses!