After 28 days, it has gained +12 total for the entire period (not per day). When I first got it, I noticed that laying it crown down gains about 2 seconds a day and crown up loses almost 2 seconds. It gains a little when worn. So I follow a routine of how I place it on the desk every night (alternate crown up/down) and am happy with the results. According to the boutique, the tolerance is +/- 1 minute per week for a geneva seal piece.
Edit: Just checked and the total accumulated gain for 28 days is 12 seconds.