Was the $ amount specified in the QDRO or just the % of the account balance? If the $ amount was specified, I say, everything is fine. However, if the % was specified in the QDRO, and you don't agree with the payment amount, then you should communicate your concerns to the Plan Administrator. If you are acting as the Plan Administrator, you should consider sending both attorneys a letter expressing your concerns. If neither responds, then you have done your duty.
The attorney represents the individual and is trying to get the most of their client. You represent all plan participants, include the AP.
Is it possible the valuation date used in the QDRO is not the same valuation date you used? If the plan is still accruing benefits, maybe additional benefits earned after a certain date were not allocated to the AP?