What does it mean by non ovulating days when doing sex

Those that did sex without the intention of getting pregnant, be it pull out or condom, by doing on non ovulating or safe days, are the days leading up to ovulation (fertile window, as shown on calendar app) considered safe days too ? Just avoid the ovulation day itself will do? And yes i do ovulation test strips usually when i see the “fertile window” on my app just to double confirm. As ovulation can be on different days, not always the same cycle day. #firsttimemom #advicepls