how much oil?

[Faustus100]

I recently purchased an 03 H2.I live in NY and drove it back from ILL.Before I drove back I got an oil change.By the time I got to NY my oil life was at 91% which I thought was pretty good.I just got an oil change from a local place 4 days ago and without driving much my oil life is at 78%!It seems impossible since I may have put on 25 miles since the change.I didnt get a manual when I purchased the truck so my thinking is that maybe he may not have put in enough oil-any suggestions?How much should I use?
Thanks