How to disable a small active meter on my Toshiba Satellite L15W B1320 computer?

The computer works fine, no hardware or software issues. It wasn't turned on for three months and then when I turned it on a small vertical black rectangle meter displays on the upper left corner of the screen. I click on it, slide the meter up and down, the numbers in white change and that's it. Nothing visible changes. I can't deactivate it. Can't find anything on the Task Menu that hints its the meter.