Balances and available funds
An account’s balance is its opening balance plus everything that has happened since: the transactions you record, plus money transferred in, minus money transferred out.
Only the account’s own currency counts
Quidough counts amounts held in the account’s own currency and nothing else, so a converted figure never quietly finds its way into a real balance. Converted totals are for looking across accounts, and they work the way currency conversion describes.
Available funds
Available funds is what you have left to spend.
For an ordinary account it’s simply the balance. For a credit card it’s the balance plus the credit limit, because a credit card balance is what you owe, so adding the limit gives you the room you have left.
If a credit card has no limit set, Quidough doesn’t show available funds for it. There’s nothing to measure the room against.