Your wallet balance is the number of unused report you have. Whenever you purchase multiple reports package, that number of reports is credited to your wallet and it is depleted as you request for Vehicle History Reports (VHR) on the portal.
Anytime you are making request for a new VHR and you have a wallet balance greater than 0, the system automatically selects your wallet balance as a payment option. Consequently, the system ensures you always use up your wallet balance before making additional payment for reports.