We have a Uniwell LX-5000 series 02 type. Last week someone entered a price change on a PLU. Not sure if this is related, however now if I want to enter a sale for 7.00 when I press the 7 key the machine beeps and enters nothing. If I enter a sale of 9.75 the machine enters that as 5.00 + .99 10% discount = .89. How do I clear this and resume the 7 key function?