Double-click test
One press showing up twice? Watch the gaps between clicks.
Recent intervals
Click twice to see the first gap.
A short gap is a clue
The threshold highlights pairs close together. It is your chosen cutoff, not a diagnosis. If events arrive 140 ms apart with the cutoff at 200 ms, the pair is marked. Set the cutoff to 100 ms and it is no longer marked.
The browser chooses its own double-click timing, so its count can differ from your short-gap count. Deliberately double-clicking is a useful way to see both readings change.
What this cannot tell you
The page sees events after your device and operating system have handled them. It cannot prove how many times a switch moved or whether a mouse is faulty. Hold a keyboard key and it counts once; choose Keyboard to inspect separate presses.
Want a speed score instead? Use the CPS test. If you are comparing deliberate clicking styles, keep those attempts in clicking techniques.