Normally, the icon that appears in the system tray shows the current CPU usage:
(https://i.imgur.com/FplpWlh.png)
But sometimes this icon is momentarily changed to an image of a balance, with a red background:
(https://i.imgur.com/H7QLic3.png)
What does this mean?
That means ProBalance kicked in reducing the priority of a process.
You can open the "Insights" tool and see what processes ProBalance acted on under the restraint count column.