Blank fields are set the cookie value automatically on the Confirm Your Purchase Screen of Market Pr

I encountered issue when I do following steps.

[step 1] After I logged in to WordPress, I enter some value on Shipping Information screen and then go to Confirm Your Purchase screen.

[step 2] Go back to Shipping Information screen by clicking on Edit link on the confirmation screen

[step 3] Reenter blank on the particular field and then move to confirmation screen again

[step 4] Then confirmation screen doesn't have blank value on that screen, instead the filed still have value entered on step 1

How can I manage to get blank fields after I enter values to the fields once ?

I'm using Market Press Plugin 2.7.