NI6003 counter become half num when write do

Dear all

I use labview to try write an counter

if only run counter task,the counter value is correct value

and i add the do task,the counter value also corrct

but when i write true or false to DO task

the counter value will become half of original value

and the value will more jitter in each loop

original one loop about 1195 ~ 1205

after write value to DO  then one loop about 575 ~ 625

pleae help me 

device:NI-6003

counter:P2(PFI0)

DO：P1(Line 0)