Failed Inspection - Brake balance?

[nj300se]

Hi folks! Just got back from state inspection and I failed for "brake balance". Specifically, the rear axle "difference left/right axle excessive" On the chart they gave me, the rear driver-side wheel has less brake (deceleration?) than the rear-passenger wheel - hence the failure. Front axle is OK as is the emergency brake.

Its a 91 300SE with just over 61K on it. Two years ago it had 59K on it and passed.

Not sure what it means, or what I should do beside take it in to my mechanic to look at. The brakes don't feel weird to me, but I guess something is astray.

I'm just hoping to get some ideas here so I can have a semi-intelligent conversation w/ the mechanic, or maybe there is a simple thing I can do to adjust as needed?

Thanks!