GS Activity Counter is a free Chrome add-on developed by Adam Roth. It falls under the category of Browsers and is specifically classified as an Add-ons & Tools subcategory.

This add-on allows users to track their activity from HLStats for the current month. It excludes data from the previous month in its calculations. The activity is displayed on the Sessions page of the respective player, as shown in the provided screenshot.

The latest version, 1.3, now displays the time even if the activity is completed. Version 1.2 fixed the issue of negative values when the activity was completed. Version 1.1 added support for all HLStats from GameSites.cz.

If you're looking to keep track of your HLStats activity on Chrome, GS Activity Counter is a handy add-on to consider.