38E: dot in upper left corner of display

[Dave Britten]

I just got a 38E, and it appears to be working fine (after soldering the crummy solderless display connection), but there's a little dot displayed in the upper left corner, above where the negative sign appears. A quick skim of the manual didn't uncover any clues. It doesn't seem to be linked to the BEGIN/END switch position (which is working - I get different results calculating PMT), and as far as I know these are fresh batteries. Anybody know what it means, if anything?