I started the application and started typing in some random numbers.
Only the following numbers will actually be entered: 2,5,8.
Pressing 3 or + opens additional operators.
Pressing 6 enters a dot.
Pressing 9 enters zero.
Pressing ? enters equals sign.
No visible actions from the order keys.
The navi key/dpad is working as expected.
This application is much better than the classic calculator. I hope you will take this fix into consideration.