Rear End Cleanup, Help?

TrailBeast said
remove that vent

TrailBeast said
This will keep the rear from getting soaked all over the tube like it is now.

I don't see a vent, just a bolt head. It looks like that fluid was pushed out where the axle tube is pressed into the center.

It definitely needs a vent, lol.

EDIT: Or is the tube thingy (technical term) the vent?