Ok, What have I done now... (904 problem?)
When a few quarts low (after a drain), I often see a false level on the stick. I expect it is from spashing/slinging fluid. After a rebuild, you must run it partially full because if you try to put the full load in first, it will start overflowing (how do I know?). You have to run it a bit to fill the torque converter, then slowly add more.