For your situation, It is basically 1000,000 executions.
Free limit of consumption plan has two standard.
First:
{The computing resources(GB)} * {the time your function execute} <= 400,000
Second:
{Total execute times} <= 1000,000
From your description of your question, the spend of unit computing resource is not very large. But not matter how small of your spend of unit computing resource, it only free for 1000,000 executions.
This is the pricing calculator:
https://azure.microsoft.com/en-us/pricing/calculator/?service=functions
And please notice that the above free limit of your function is based on plan, but not function app. So if you have two function app, and both of them are using the same plan, then the free limit you need to calculate both of them.
Let me know whether this can answer your question.:)