Altitude problem

I'm making PMDG 737 NGX overhead panel. I'm Using FSUIPC and Mobiflight but FSUIPC altitude output is not getting a valid value after 32700 (I set the Mobiflight parameters as Int - 4 Byte).

Also, land alt output readings are always stuck between 0, 1, 2, 3 as I turn the rotary encoder. Is there a way to fix it?

Thanks in advance.

Altitude problem is okey
Code
if current value is<0
set it to $+65536
else set to it $