When selecting the option 'Keep My Existing Number' there are 2 different options: 'My number is already active' and 'My number is not active'; what is the difference?

Option 'My number is already active' should be selected when your number is already active with another operator.
Option 'My number is not active' should be selected when you just got the number assigned to you company by the local regulator and is not yet activated on a telco operator.