Maybe a bug in calculator!
In iOS 18, a new calculator is serviced, but it calculates wrong as seen in the picture.
Question marked as
- What Language & Region is your device set for?
- Under Settings > General > Language & Region > Number Format, you may have the decimal listed instead of the comma
It appears to be related to your region since you have the comma on the last row of the calculator, where the US region would show the decimal point by default.
I got 12960 in the US.