It depends which part of the report is negative but it usually means more money went out somewhere than came in, so this could be due to someone refunding a large amount of money or voiding off things that were never sold in the first place. It is almost always caused by incorrect entries.
If anyone needs more information, the Sharp XE-A102 manual is here:
http://the-checkout-tech.com/manuals/cashregisters/Sharp_XE-A102_operating_and_programming_manual.html
Registerman, July 2011
