Your number health score is a single figure between 0 and 100. It answers two questions at once: how comfortably your WhatsApp number is carrying the work you have given it, and whether WhatsApp is currently restricting it.
A number with a good score connects quickly and starts sending sooner after it comes online. A number that is carrying too much gets slower at everything: it takes longer to start up, and messages wait longer in the queue. And a number that WhatsApp has restricted cannot be rated healthy however tidy it is, because the most useful thing the score can tell you at that moment is that WhatsApp has already acted.
Where to find your score
Open your dashboard and click on the number you want to check. Near the top of the page there is a row of small cards with figures, and one of them is Health score.