Selecting D on the keyboard when the cursor is in Add Deduct column will allow a minus figure to be entered. Selecting A will revert back to positive figures.
Negative figures cannot be added in the Side Cast area. The Annotations can be used for calculations if required. For example, if you enter '4-3=', the system will complete the calculation.
That will allow you to do addition '+', subtraction '-', multiplication '*' and division '/'.

