What is the 0/30 mean on Escape hives?

Can anyone elaborate what the 0/30 means on Escape Hive maps?

The 0/30 is extra bonus card drops you get for beating a chapter of escape as well as finishing the escape. Normally you only get 1 card per checkpoint, however you can get bonus card drops from the reserve if you have any more to regain, so if your at 0/30 and complete 1 checkpoint it will jump to 1/30 and you will get two cards for that checkpoint instead of one. once it hits 30/30 you will go back to getting 1 card per checkpoint.