Happy to clarify! The documentation for the Get recently created contacts method contains everything needed to use the endpoint.
While the endpoint's title implies it will only return contacts within a specific "recent" timeframe, what it really does is get all contacts in reverse chronological order, in sets of 100. Thus, if you wanted, you could continue to page back to the very first contact created in your account.
Most developers using this endpoint will have their system check the
addedAt timestamp (in milliseconds since epoch) and stop when the value matches the beginning of the timeframe they are looking for.