While the numbers are nice, if some outages only impact a subset of customers and your monitoring accounts aren't one of them it's hard to determine how good your monitoring data really is. If he was impacted by a 12 hour outage and you only show ~2 hours that's a really significant difference.
I guess it really depends on how you monitor and how comprehensive it is. Do you monitor from multiple ISPs on different network paths in multiple regions/countries? Do you monitor each of the services under different load conditions and monitor multiple accounts? Sometimes "up" only tells part of the story.
Your monitoring sounds really comprehensive. That's a very cool way to advertise the service it's built on. Do you monitor service providers for outages that reduce capacity or increase latencies but otherwise the service is "up"?
https://cloudharmony.com/status-for-aws