They could have done it to the extreme -- show the numbers for the past hour. Then they could almost always report 100% uptime. And if they ever went down, wait an hour, then go back to reporting 100% uptime again.

They could have terrible uptime 2 months ago and you wouldn't see it in their status page, because it only showed last month's.

Parent post was saying that, without taking into account the entire year, you can have one month that is terrible and the rest quite good.

The measurement in question is supposed to be about consistency.

Depends on the month...

31 versus 28 days.

Or if they have 100% for six months and then 99.97% for one month the long-term average would be better.