It means the dev team added code to fix data in saves that might have been causing problems. There is nothing to worry about, it just means the save you are trying to load hasn't been updated to the newest version. For instance I added some code to the load process last week that cleaned out any preg objects on sera since they shouldn't exist (npc preg is handled differently). Someone imported a save from years ago that had a preg object on her from a very old bug. Any save from before that change would get the warning. I think Geddy just did one for inventory issues as well.