Program S7200 position module EM 253

I want to program S7200 position module EM 253 but….
I am feeling some problem ...
I am using POS0_GOTO instruction for drive AC Servo motor. When I enter speed or position data through HMI in POS0_GOTO instruction then it display...

If
Enter zero then 0.0 data show in register and
If
Enter greater then zero value then ' NAN ' data in show in register
Due to this error I can change speed through HMI............

But if I enter any constant number in POS0_GOTO instruction for speed and position then AC Servo motor run properly...

Please help me in this problem...