Specificity of X-Poll-Interval

Events API allows polling using an ETag header and will return an X-Poll-Interval header to let the client know how often it can poll.

What is the specificity of X-Poll-Interval?

Does it relate to all requests by the user-agent? (eg. at most one request per 60s for this user-agent)

Does it relate to the individual resource being requested? (eg. at most one request per 60s, for each network of repositories being polled)

Something else?

(For context, I’d like to track changes to certain files across a range of repositories in near-ish real-time. It seems to make sense to regularly poll for push events to the relevant repositories, then check on whether any of the relevant files changed.)