The renumber is only restricted if your settings are restricting it (dumbest option in Manager)
the option is in System - Telephony - SM - Local Number length
you can delete it and it allows anything or set it to your new value to make it work.
If you renumber via Manager tools it will fill any gaps you have in your numbering plan (sucks)
So if you have 100, 101, 103, 104 and 105 and renumber them to 200 number you will get 200, 201,
202, 203 and 204 then missing 205 instead and 203 and 204 are also not matching the old numbers.
Addendum: it will skip users that have no extension programmed
Useless tool for (I guess) 90% of renumbering jobs
Joe
FHandw, ACSS (SME)
Remembering intrigrant 2019