Hi Wen

If some of those users has the orgidnumber mapped to 2 (SCL), would they be mapped correctly?

The Audiences and reports that use the Orgidnumber would be mapped to the existing Orgid so would need to be changed to reflect the new orgid. Audiences and reports mapped to the hierarchy item (organisation name) would include the records with the new organisation name and number as it is still mapped rather than based on the value.

As long as you replace all the old organisation ID 22 with the new organisation ID  2 and modify the reports and audiences that have the organisation ID in it to organisation ID 2 then you can reuse the organisation ID of 22.

Hope this makes sense.

Craig