A few hundred, because that is what is being provided by the service.
"I found a billion hits, but I'm only giving you two" is in no way a good defense. It is blaming the user for a completely reasonable interpretation of the language -- weasel words are not appreciated by people.
You think a for-profit company should invest in a feature/edge case that will never be used in an earnest or useful way?
The idea that you would earnestly search through 400 records only to not find what you are looking for --but the 401st record would-- is just not a realistic use-case.
No, I expect them to list the number of results within an order of magnitude of what is available for the user to review, which would be an accurate and reasonable report for what is provided.
And if they want to offer your proposed crazy edge case as a service, folks needing it are willing to pay for organized information that is deep.
I agree this is not a common use use case. But it is absolutely a realistic edge case and I used to do it. It is exactly these edge cases that make software truly useful. Multiple search engines are as good at the common case.
"I found a billion hits, but I'm only giving you two" is in no way a good defense. It is blaming the user for a completely reasonable interpretation of the language -- weasel words are not appreciated by people.