I am using the erase tool to remove the area covered by one feature class (269 sq mi) from another feature class (1617 sq mi). 1617-269 = 1348. However, the result of the erase gives me a feature class that covers 1391 square miles. I expect a little discrepancy, but 43 square miles difference seems like a lot to me. The the only setting for the erase tool is XY tolerance, which I have played with, but it has not helped me. Is there anything that I can do about this?