If you change the filter, it needs 4.5 quarts.
If you only drain the pan, and keep the old fiter then you need 4qrts. Just like allready said. Autozone is'nt exsactly right.
If you did'nt allow some settle time after you shut off the engine, you dont let the oil that was all sloshed around to drip off the dip stick.
Run engine, shut it off, wait 5 minuets then check it by wipping it clean first.