No. Aqua will not automatically charge your account for using more units than you have purchased.
While the account is over capacity, the Aqua Wave console returns only partial results. The same limits apply to API usage. In addition, an alert will be presented at the top banner of the Aqua Wave console.
For example, if your plan allows 10,000 units and you are consuming 15,000 (50% over capacity) then a CSPM scan report with 500 scan results will return only the first 250. Once your account returns below the 10,000 unit allotment, the same scan report will return all 500 results. The results are never lost, even during periods of overcapacity.
Please note that Aqua Wave automatically resumes normal operation as soon as the overcapacity situation is addressed. Addressing overcapacity can be done by subscribing for additional capacity or by reducing the unit usage, such as by disabling unneeded CSPM cloud accounts.