Here is document(refer to Step 7 - Configure a Daily Use Quota
for the details.) about daily memory-time quota
.
In short, when using Azure Functions consumption plan
, it offers near-infinite scale to handle huge spikes in load. But that does also leave you open to a "denial of wallet attack" where due to an external DoS attack or a coding mistake, you end up with a huge bill because your function app scaled out to hundreds of instances. The daily quota allows you to set a limit in terms of "Gigabyte seconds" (GB-s).
For "Gigabyte seconds", you can refer to this SO answer.
Hope it helps.