@fluxwatcher a few days ago, I couldn't understand why MATE Calculator was responding strangely to numerical input.

After a few failed attempts: I stopped trying to use KCharSelect as a calculator.

Then, I couldn't understand why the true calculator was responding strangely to numerical input.

After a few failed attempts – including random clicks on things that I had not previously noticed in MATE Calculator: I stopped trying to use KCalc as if it was my MATE.