counter returns garbage values

I am using cDAQ 9184 and 9401 Digital I/O card,I am using the counters available for frequency measurement(pulses are generated by a hall sensor,whose frequency i want to measure to estimate DC motor speed.But the problem is that counter returns garbage values.I have tested the card and its counters they are working fine.What could be the possible causes of this happening?

attaching a VI snapshot.
Please hep me out at the earliest. :)

Thanks and regards.