F23A1 balance shaft question
 

Working on F23A1 engine. 1st timing belt replacement. Trying to follow directions to a T, haven't taken belts off, only removed crank pulley & timing covers. Put bolt in service hole to lock balance shaft. All TDC & timing marks are 1 tooth off with bolt locked in balance shaft. Could this be factory mistake or could balance shaft sprocket have jumped a tooth?