Max limit was set to 77 and it continued at 75 which could have been dangerous. Speed limit in that section was 60.
You went 15 miles over speed limit on AP. Doable, but not a good idea.
I will give you an advice to make your Autopilot experience more enjoyable more useful. I have driven a lot of miles in autopilot - over 60k miles I would think - over the last 4 years over all sorts of roads., not just highways. I turn on AP almost every time as long as there are lanes.
But the one thing I do is, I set it mostly at 5 miles an hour than the speed limit and sometimes at +10 miles if the roads are marked well and straight, but never greater than that.
At speed limit you can close your eyes (don't do that, but you get the idea). But I understand it is not possible to go at speed limit except in city roads. In fact when the traffic is flowing at speed limit, I really enjoy AP the most.
At +5 it is fantastic, which I do when the speed limit is 65 or 70, but I watch near curves and when the lanes are iffy.
I go at +10 only on some roads where the speed limit is unreasonably low at 55 or 60, and the roads are pretty good. Never more than that on AP. But I watch extra careful around curves and lane lines.
There is a reason each road has a speed limit based on the terrain and other conditions. Now you may be pressured to go at +15 when the traffic is light, but don't do that. You are not really saving any time.
On curves, AP reduces the speed only sometimes, often it misses it. it is not using map data, and so often it encounters the curves at higher speed and struggles.