About this Add-on
The toolbar's default position in Firefox 2.x and 3.x is at the far right in the menu bar. In Firefox 4 and up, the default position is at the end of the tab bar. In both cases, you can move it to where ever you want by right clicking on the toolbar and choosing customize and then dragging it anywhere you want.
Advanced formatting of the text label is available by checking the option in the options window (right click on label and choose "options"). This allows reporting the current tab number as well as other information about tabs. Hover over the "format string" label or text box for a tooltip explaining how to use advanced formatting.