I read through the manual and old posts and found a solution that finally seemed to give me a format for my counter.
seconds and milliseconds are displayed like this "2:45"
Until this was displayed "1:100"
Here's the action:
"Average:"&" "&Date.ToTimerSeconds(IntervalName.ResponseAverage)&":"&zeropad(round(Date.ToTimerMilliseconds(IntervalName.ResponseAverage)/10),2)
Now I don't understand what's happening. If you do please explain. Because I would really like to understand ;)