If you attempt the auto update or auto update multiple controllers with same USB you must delete the 00 folder that is created during the backup sequence or your second auto update will fail. You can auto update for example v8.20/1 to any auto update v8.20/**
If you want to update from v8.20 to 8.30 you can do this also but not from an auto update media. You must use a core load from 8.30 and perform the auto update.