When an item is removed from the End User Recycle Bin, it is stored in the Site Collection Recycle Bin for the remainder of the 30 days. The items in the Site Collection Recycle Bin do not count against the site quota and its size is limited to 50% of your site's quota. If you exceed the quota, then the oldest items are purged to make room for new items. Only site collection administrators are able to recover files from the site collection Recycle Bin.