Fishy odometer

My starter stopped working about a month ago and i went to a junkyard to save some cash and get a used one. i did the repair myself and my first attempt ended in failure. I wired the starter wrong and it burned out. I got a new one and it all went well. my problem is that before i changed starter my odometer read ~87000 miles. after the repair, within a few days, it read 102000+. what happened here? i’m the cars second owner but i haven’t done a carfax yet to see if the odometer had been changed.