What do the Pen and Pencil buttons in the bottom-right corner mean?
When the Pencil button is selected, entered numbers display as annotations for the possible values in a certain cell. Entering the same pencil number again will remove it from that cell. However when the Pen button is selected all entered numbers are definitive. You can alternate between Pen and Pencil by using the Right Soft Key (on most Windows Mobile and Symbian devices) or the # key in Symbian Series 60 and UIQ devices.