I have ARB covers front D30 and rear D44. Rear capacity was about 2.5 quarts and front just under 2.
I originally had less in the rear after re gearing listening to what was said on here and when I changed it last week, realized it was too low and pretty dirty. I have plenty now...

The ARBs have a dipstick in them. I have them filled about 1 1/2 to 2 inches up on the dipstick. The rule is to scratch a line on the dipstick at the fill line hole on your stock cover.