How can to enter code in the unit. It seems that only a single digit is available.
The PIN-Code parameter shows a single digit which is "1" by default . Simply turn the wheel to reach the value you want to use as a code. the value does not stop at "9" and by continuing turning the wheel clockwise, you can reach higher numbers of 2,3 or 4 digits.
Once you have set the right PIN-code, go the the previous Parameter (security Lock) and press OK to activate the lock.