add opens Stripe Checkout. Minimum is $10. After you pay, wait for the webhook and re-check compute credits. A pending Checkout does not add spendable balance.
The dashboard credits page shows the same ledger.
How spend works
You buy credit first. A run is refused if the hold would exceed remaining credit or a spend cap. Billing is started minutes while the machine exists, plus the platform fee on that usage. Failed boots that never start the machine are $0. See Billing. Do not copy a fee percentage from this page. Use Pricing andcompute runs receipt <run_id>.