If you do not have enough funds in one of your wallets, you can combine them with other wallets. To merge wallets, in the purchase confirmation window, check “Use a different wallet if there are insufficient funds available” box. The missing amount will be deducted from the wallet with the most funds.
The User wants to purchase a product from a BTC wallet, which costs $20, but there is not enough amount to complete a payment. He/she uses “Use a different wallet if the current one does not have sufficient funds” method. He selects a BTC wallet with a balance of 15 USD, the missing sum of 5 USD will be collected from a wallet with the highest balance at the moment.