help to check my project convert digital signal (count edge ) to RPM

I want to get RPM from Motor use rotary encoder

and insert to colom N on table measurment..

but i doubt , my project is true or wrong..to convert digital signal ( pulse ) to RPM

i used count edge on USB DAQ 6008

Please help me to check in green border..

this is project i create

i copy at this article http://www.ni.com/example/13580/en/