As you said “if you get a positive result”. It’s true, if you ignore the 99.9% of the time the test is correct (true negative result), then you can say the test is 84% wrong.
84% of people who got a positive test result will end up telling their family "it's OK, the first test was wrong, my baby doesn't have a 1p36 deletion after all". The 99.9% of other people who got true negatives are important from a test design perspective, because specificity is closer to the actual levers you can pull on, but it's not super relevant to the decisionmaking process of someone who gets a positive result.