Q: ipad mini not registering storage upgrade

You didn't need to upgrade iCloud storage. You needed to delete content on the iPad in order to upgrade. iCloud is for backups, not for storage. You need more space on the iPad itself.

Delete some content from the iPad and then try again. Read this for more information.

http://support.apple.com/kb/HT5772

iCloud space does not affect the iPads physical storage.    You need to delete content from the iPad itself to make room for the update.