The ONH isn't necessarily relevant. You're looking for the range immediately before the open. This is where traders have found equilibrium (if you're not clear on what that is, Ctrl+F Wyckoff's course and the pdf). The disturbance of that equilibrium is where the opportunities lie.
The "ish" part of 4415ish is correct. You're not going to get a rigid line. Trades are going to bounce around a bit, in this case, from 14.25 to 14.75. At 0814, traders make a serious effort to get past all this. They get as far as 16.25 and fail. This does not mean that the upper limit is raised to 16.25; it means that the importance of the lower one is confirmed: this is the level beyond which traders can't/won't get.
When is the next attempt to get past 14.75?