Okay - I'm going to reveal my statistics ignorance here - but if they did get a false positive, how does 0.0% fall within the range of possibilities (or is that allowing for it might be 0.0499..% or lower?)
But, yes, you are entirely correct as to the practical meaning. 0% itself is impossible, but 0.0...1% could still happen.
Which can't lead to a "true 0%", since there's no such animal. But it could mean that all of the tests gave correct answers, in the trial.
> Specificity samples were derived from de-identified excess serum specimens sent to our clinical virology laboratory in 2018 and 2019.
So...not five years ago, and it is even possible that a significant number were from late 2019.
For the things considered here, the point 0 is measure zero so open starting at 0 and closed at 0 are the same. L
(More likely, 0.04% or similar is being treated as 0.0%, but I haven't done the maths to confirm what the number would be)