LAUNCHXL-F28069M: InstaSPIN LAB13b Problem

Tool/software:

I use  LAUNCHXL-F28069M and BOOSTXL-DRV8305EVM to test lab13b, but I have problem for this

I set 

gMotorVars.PosStepInt_MRev = 1

gMotorVars.PosStepFrac_MRev = 0.5

gMotorVars.RunPositionProfile = 1

Then the motor didn't move 1.5 circle

Is there any solution?

THX