Last year, when Apple closed the pay-service MobileMe and replaced it with the free iCloud, Apple gave an additional 25GB of storage to former MobileMe users as a thank you. This “gift” was supposed to expire in September this year. But now Apple wrote that they will continue offering complimentary storage for an additional year “As a thank you to our former MobileMe members who moved to iCloud, we have extended the complimentary storage upgrade they received until September 30, 2013. This extension applies to accounts moved to iCloud between October 12th, 2011 and August 1st, 2012.“
Apple explained that, your complimentary storage upgrade was based on the amount of MobileMe storage you were paying for when you moved to iCloud. You were granted either the 10GB, 20GB, or 50GB storage upgrade.