in this option do a 6 digit code where the first 4 digit code IS the one you actually want to use, and the option "unlock phone without pressing OK" should appear bellow already checked, if not check it.
With this option checked, highlight the password as if you would do with any text, it should be hilighted blue, leave hilighted ONLY the last 2 digits.
With the last 2 digits highlighted, use BOTH of your thumbs to press backspace/x AND Continue AT THE SAME TIME, this should take you to the next screen.