I don't think we can do much better than the calculator. There is also a full explanation of the rules in How does the Schengen 90/180 rule work? but they are somewhat complicated, there is no way around that.
But I can at least offer a quick rule of thumb: If you stay for a full 90-day period out of the Schengen area, then you can definitely reenter for another 90 days, provided you fulfill all the usual conditions. It might be possible to reenter earlier if you made several short stays with breaks in-between and that's why you need a calculator to figure it all out, but 90 days after the last time you were in the Schengen area is definitely safe.
The reason for that is that after 91 days, the first day of an earlier 90-day stay has to be more than 180 days in the past. So you have at least one day left. On the 92th day, then the second day is now more than 180 days in the past and you still have 1 day because it's a sliding window. And so on, for 90 days in a row.
Something similar happened in your scenario. On the 25th of August (and after that date), the February stay is already more than 180 days in the past so it does not count, which means that you have used only 76 days (and not 85). That's the easy part. But after a few days, on September 2, the first day of the March stay is also 180 days in the past. So you can use those days again, one at a time, following the sliding window principle I just explained. And the total length of stay allowed (either then or now) is 14 (that's 90-76 available on the 25th of August) + 17 (the length of the March stay sliding out of the window starting on September 2) = 31 days.
And it's only in December that your last stay will begin sliding out of the 180-day window. So if you don't come now but enter on the 24th of November instead, you will have a full 90 days available. Why the 24th? It's because 181 days after the 28th of June is December 25 and you have your 31 days to bridge the time between November 24 and December 25. (If you enter all the dates in the calculator, you will see that on November 23 you only have 31 days and on November 24, you suddenly have 90 days. That's because if you enter the area on November 23 and stay 31 days, there is still a one day gap before you can reuse the 59 days of your June-August stay.)