Yes, the $5 pending charge you see after updating your API payment method is a temporary authorization hold on your credit card. This is part of the process for setting up the pay-as-you-go API plan. The pending charge will be reversed within 7 days.
Rest assured, you'll only be billed for your actual API usage at the end of each calendar month.
If you have any questions, please send us a message via our chat widget in the bottom right of your screen and select the "Billing" option.