Confused

Ok so I've been ttc since August every other month I take opk and the months I don't take opk we kind of wing it bc everyone's like stop testing just let it happen so we've tried that too.. I follow and chart everything in the glow ap and I've become a little confused my cycles are 27 or 28 days on average the app tells my my highest fertile day was Wed but I only had a 12% chance Wed of becoming pregnant 23% Thursday and 30% Today (Friday) so how was I most fertile Wed but have a high percent today?? I've baby dance Tues Wed Thurs and will also today so I got every day.but I'm having trouble understanding all this ..help!!