...
When you are using Contents the Availability Check helps you to check if the selected contents are still available.The field Requested Contents should be filled by you in the Media Configuration or Campaign Item and the Available Contents are
Please check out our Wiki page about Contents to understand the workflow of Content selection in preparation for the Availability Check.
After submitting the Availability request you see the value Requested Contents which was filled by you and you see the Available Contents shown due to the highest availability possible.
...