Been there - certain aspects in the database are permanent... I have talked to support several times about these "ghost" entries, and deleting them from the console doesn't always get rid of the bogus data. To be absolutely sure the best option is to delete it from the DB, then re-create it correctly.
So when you increased the range size from a /24 to a /23 did you click add the IP address range. When you click this then you can add the IP address of the whole range and it will fill in the missing IP addresses. consequently when you go from a /23 to a /24 then IPAM will automatically delete all the IP address and information that is outside the new range.