Hi jeet
It means you can bring the number you hold prior to moving to 48, over and use it, as opposed to getting a completely new number on 48.
During registration with 48 (Everyone receives a 089 sim card from 48) - if you wish to keep the number you have already, you apply for those on the 'Move your Number' section you refer to...
I believe you can also apply for this at any stage at a later date by contacting support.
🙂
