This is a small and not always reproducible "error" in the Aquasuite.
I have observed this phenomenon several times when I want to generate a new maximum value in the Playground, i.e. when I take the output of the virtual sensor as an input again and forward the maximum value between the current value and the formerly max. value to the output.
When I create this (respectively a new) virtual sensor, the output (in the above case: 60,75°C) sometimes fluctuated between the maximum value (60,75°C) and the current value (45,50°C). After a restart, however, everything is as it should be and this phenomenon never occurs again (for this new virtual sensor)
The statistics evaluation stored in the Aquasuite will have a similar structure to my virtual Sensor (maximum value) described above and your "jumping" from Zero to the max./min. and average should not be there anymore after a restart of the PC or Aquasuite and AS Service.
In my opinion, this has something to do with the update rate (one second?) of the inputs and intermediate storage of the values as well as the time needed for processing the logic for the values.
The evaluation of the data sometimes hiccups a little, but this calms down after a restart (at least for me).