This message appears because 3 incorrect attempts have been made.
'7' is the number of remaining attempts. (After the 10th attempt, the radio will be completely locked.)
To resolve this issue, you need to leave the radio switched on (showing '7 SAFE'). After some time (up to 1 hour), the display will change to '7 - - - -'. And you will be able to enter your code.
A.R.S.
December 2012