Paolo,
You will need to do 2 things:
(1) Set range for FS Variable FLT_ALT
(2) Set format for TextLED
Here is how to do (1)
Fire up FSVariable.exe.
Open FS2PhUIPC401.ini using menu (CTRL-O).
Set the high and low values to values you need.
Note: internally pmSystems stores 1,000 feet as 100.
For example entering -100 for low value and 4500 for high value will restrict flight altitude value from -1,000 to 45,000 feet.
Make sure "Wrap values" check box is clear.
Press Save icon.
Number (2):
Fire up FS2Phidget.exe.
Select "Configure" radio button.
Click on TextLED row in Phidget list.
Click on Text LED component assigned to FLT_ALT.
Press "Calibrate" button.
Enter Format as
0000"0"
Press OK.
Regards,
Alan.