Well I don't know if I've overfilled, underfilled, sidewaysfilled.... it's so difficult.
For example, 2 weeks ago I drove a distance of 28 miles, mixture of stop-start driving, lots of gear changing. Did as Hyundai GDS instructs and ran the transmission through each gear, held it for a few seconds, then placed in neutral with engine running, and checked - bit bubbly but appeared in between hot low and hot full. Okay, good enough, will top up a bit when I have ATF. (Which I didn't at the time.)
Last week, drove a distance of 90 miles, all motorway with very little gear changing. Again ran through gears, held, in neutral etc, and checked - looked massively overfull this time, well above the "hot full" on the dipstick but only on on side of the dipstick
Dipstick in and out umpteen times, still only on one side. Gave up and drove home. Annoyingly I can't check it at home because I live on a fairly steep hill where I park so need to check when i'm out and about on a level surface.