8 3/4 venting oil from the vent. seems odd.

Took the car out for the first time since I disassembled, cleaned and serviced the whole rear axle assembly.
Ran it briefly on the expressway.
Then noticed that a very slight amount of gear oil seeming to have come from the vent.
I pulled the plug and some did come out so I may be over serviced?
What say y'all before I run it again?
Pull the plug and let it drain till finished?
I'm just wondering how one can possibly put THAT MUCH "too" much in from the side hole.