Quote from Pekelo:
You do whatever you want, but the rule is based on the cash close. There can be 3-4 pts difference during that 15 mins between 4 and 4:15.
For example let's say yesterday ES is at 94 when the cash closes, then goes up to 97 by 4:15 pm. Now this morning, I would have already closed my longs from overnight around 93, but you would still be holding it. Since the gap has been closed according to my view, we could fall from here, 93ish, and you would only get a breakeven or a small profit/loss, depending on where your stop loss is....
About premarket gapfills: There is again a difference between a 2 am fill and a 8 am fill. If it is rather close to the open, I count it as RTH and I don't necessery expect to do it after the open....
Edit: Here we are, 8:37 and the gap has been fully filled at 94.5... Now we can tank if the market wishes to do so, the rule has played out...