apparently, this is this particular "card"'s manner of having all your banking in hand. It's a secured card and checking account in one.
The "Cash Account" is your checking account, which you load with direct deposit or other manners. The "Credit Balance" is apparently the amount you can spend in a debit/credit card style.
Basically, they secure your "credit card" with a deposit from your "cash account [read checking account without the checks]" The automatically debit your checking account for the minimum pymt. This is apparently irrevocable because that account is the ONLY way you can pay them.
Your available credit is the amount of your credit balance PLUS whatever funds in your checking account.
Say you have 1000 in your checking ("cash") and 500 in you credit balance but you want to buy something that's 1495. They will transfer the extra amount from your checking, increase your credit limit to 1495 and you can buy your thing.
but now, your checking is empty and you've charged up the card to the limit. So you now have a higher limit (once you pay off that bill), but you've also used the money in your checking account.
It's a glorified debit card that reports to the CRAs.
"...what good do your words do if they can't understand you??...."