G22 gear oil question

[In2ice]

I just bought a G22 a few weeks ago. Trying to do the right thing and check to make sure all fluids are clean and filled. I pulled the gear oil rubber cover and gear oil started to pour out. From everything I read you are supposed to pull the cover and fill it "until" it pours out and then replace cover. Does this mean that there was a lot of extra gear oil? I didn't know it the rear lean caused by the lift made the oil pour out or not. I quickly replaced the cover not to drain all the oil. How do you fill it if it pours out when you pull the cover? Should I pull the cover again and just let it run out until it stops and then replace cover? Just want to make sure there is still enough oil in there. It drained out about a half cup before I was able to replace the cover. Thanks for your responses in advance.
-Allan