Viewer is not supposed to go -10°C, because 10°C is min for every case.
What I think happened here was push level change without server response, so you THOUGHT you were in the right push.
This has been happening to me a lot since last Server issues.
So, when I'm changing push I always go from the push level I am to neutral and I wait until push icon disappearing (repeating this process how many times is necessary to get that icon changed), then I change it to max or min.
These are the icons I'm talking about: