EU 90-180 rule and overstay

Your situation is actually very simple. You need to stay out of the Schengen area for 90 full days, after which you may stay for another 90 days, at least as far as this rule is concerned. So on October 25 (not 26), you could be admitted for a 90-day stay (if you are admitted at all, obviously). The rule is stated in a somewhat confusing way to counter an earlier interpretation of the EU court of justice and deal with some corner cases but that doesn’t make a difference in your case.

Note that the 90/180 day limit is not the only restriction on visits to the Schengen area. Among other things, border guards are also supposed to evaluate the purpose of your trip and your ability and willingness to leave the Schengen area in case. Your earlier overstay could raise questions about that (although the Covid-19 situation could also work in your favor).

In other words, the overstay doesn’t change anything to the application of the 90/180 maximum stay rule but could be an issue in itself.