Oil lever check?

This seems odd but Ive put about 500 miles since getting the 87/4.0 and have changed/checked the oil about 5 times after it sat overnight and its always right on the money. Today I fired it up to move into the shop and decided to check it before I head out and its a quart low after it sat for about 15 mins. Being the oil filter is upside down does the oil generally drain back out and thus the Ok read on the stick? Couldent have burned a quart in 150 miles..... I hope.