I mean, what qualifies as “being up”? If some random link in the middle of the Internet goes down, and you suddenly, for 30 seconds, are unreachable for the few hundred people going through that exact link because it happens to be the best path between those people and your server, can they claim that you have failed to provide adequate uptime? If such a fault happens, are you then responsible to troubleshoot it? I say no. The Internet is the ISP’s responsibility, and the only faults actually meaningful to report to your ISP are the repeatable or long-lasting ones. Small stuff like this is not worth anybody’s time (except ISPs) to go digging into.