Hi. That is a system error. Press clear (CLR) button to remove it. If it happens again, you might need to check the settings in your manual. If you have lost it, one of the users has the manual here:
https://the-checkout-tech.com/manuals/cashregisters/Towa_AL-400_and_Geller_AX-200_Operating_Programming_manual.html
Registerman
December 2015