Thanks for the reply. Sorry I didn't make myself clear. Maybe this picture can help. As you can see, the unit size is 14879 GB (in reality there is 16 TB but I left a disk out of the RAID for testing) and there are no logical volumes defined. Still, the free size available for a new volume is only 7434.94 GB.
Is the RAID controller rebuilding or has been expanded and has completed? If not then wait till it has. If it has and is completed then try restart the system to see if the free space is now available.