There are only two theories being seriously considered: lab leak, wet market. Therefore I think it is reasonable to expect a probability of at least 90% that it is one of these two theories and not a third theory that no one is discussing. So if we have over 90% confidence that _either_ "lab leak" or "wet market", and we believe that "lab leak" is the _most_ the likely cause, then it follows that we must estimate the lab leak theory to be true with at least 45% probability. Maybe you could say "low confidence" if you're 45-80% sure, and "high confidence" if you're more certain than that.