"Present balance" is the total amount of funds you have in your Dosh Wallet. This balance includes any pending cash back. If the cash back is in a pending state it can't be withdrawn, until the qualifying transaction has been cleared. Once the qualifying transaction has cleared, the pending cash back will no longer be in a pending state. It will now reflect in your "available to withdraw," so you'll be able to withdraw those funds.
In your Dosh Wallet, "available to withdraw" includes the amount that you're able to transfer. This doesn't include any pending cash back that hasn't been issued. You must have at least $25 in your "available to withdraw" balance to be able to withdraw any funds. If your present balance is higher than your available to withdraw balance, then you must wait for your pending cash back to clear.