"Present balance" is the total amount of funds you have in your wallet, including your pending cash back. This pending cash back is released when the qualifying transaction has been cleared by your credit card processor. If the cash back is in a pending state it cannot be withdrawn, until the qualifying transaction has been cleared.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.
*Please Note: For in-store purchases please allow up to ten days for cash back to be issued and up to ninety days for any online cash back.