Sharp ER 1970?

I have two problems with my tills.
Firstly, On re-programming the buttons, I have noticed that one of the buttons is showing a minus sign before the price. In normal service the button comes up with a error when pressed. How do I take off the minus sign??
Also on another till, the depts should run 1-25 (button numbers) but on this till dept 1 is showing on the first 2 button, so I only have 24 depts. How to I change that??