If all you want is to display the tab count, it will deliver. I had a little bit of a hard time making out the text on the badge but hovering over it, I could read the tooltip/pop-out text easily enough.

This addon does not have a Preferences section so if you were hoping to customize background/foreground colors or increase the font size, better look elsewhere. For those use-cases, you might try: 'Tab Count Icon by lllusion3418', 'Tab Counter (Tilwa fork) by tqdv', or 'Tab Counter (fork) by vhfmag'