The "Process Holding Tank now" link will mark any block assigned to "Holding" as "Available". This command will process ALL addresses assigned to "Holding" depending on their age. The default time for release to "Available" is 30 days. If a block has not been in the holding tank for that specified length of time, it will not be released using this feature (it can be released . The This is customizable via the Admin configuration file.
show screen of admin settings area as well