5000mah 2s lipo, discharged to 6.6V??

[Appie53]

Dear Guy's, need some advice, still trouble with my lipo's. When pack is discharged to 6.6V (5000mah pack), can I say that approx 2500mah is used?

Used this pack today, my shortcourse stopped after 2 min, still at 7.9Volts.
So discharged it with my lipocharger to 6.6V, still got 2500mah out of it.

I don't get this atall, can it be that my esc got to hot? and stopped?
Lipo buzzer did beep after 2min, set at 3.3v per cell.

Confused, confused. Hope for your expertise on this, Thanks again,..Appie