Not a problem, cloudhopper!
I found the solution by accident, but when I did some digging around, I think I found out what caused it in the first place. In a comment at BAStat’s home post at Asymptomatic, of all places, staring us in the face for the last month. (That link points right to the relevant comment.) Someone found that this field was set up to be unsigned in the BAStats.php file. By altering the file at the section described in the link above, you should get a setup that stops this behavior.
A little further down among those comments, Owen seems to find this fix workable, with a reasonable caveat:
The method described for changing the default seems reasonable if you have some knowledge of PHP.
Dona€?t come running to me when you screw the pooch….