If you did not notice any change in how the transmision shifted or operated than there likely is no damage. Just like you can run an engine a quart or more or heck sometimes I've literally drained a shot glass of oil and they ran fine before and after. The problem is when it gets low enough that the trans can no longer suck any fluid. if theres no fluid theres no pressure and the trans slips. That is when there can be a problem!
Like I always tell the new guys at work, "it takes as much as it needs to read full on the dipstick!"