Currently Being ModeratedOct 8, 2013 7:27 AM (in response to freitaslaf)
The storage is per iCloud account, independent of the number of devices involved. If you had 20GB which has now reverted to the free 5GB you were presumably an ex-MobileMe subscriber who received the free extra storage until 30 September.
This has now expired. If you have less than 5GB data in iCloud then your storage simply reverts to 5GB.
For instructions on purchasing additional storage please see