I use a macbook pro with isoburn as well. I have also burned with imgburn while on windows laptop.
So ur ihas has been flashed with Burner max firmware and rip has been patched prior to burn using abgx1.0.6.
Understand ur numbers do drop especially if this is one of ur first burns.
Ur numbers could possibly be a result of the media u chose for the xgd3 burn.
I myself use mkm003's with excellent results.