I read it in the "we have now gotten it up to X" sense, such as "I'm now up to my 5th beer"

except reliability reduces a total, not sum integers like beer count.

if I write a shell script with a scp line right now I can tell you it has 100% reliability. up to X% reliability means that "in the very nice and controlled environment, with the own devs attacking every production problem, trying to get 100% got us up to X%"

Except that is clearly not what they where trying to communicate.

That's the way to read it.