The numbers a practice actually runs on.
A practice can be busy every day and still be broke. Collections that trail production, overhead that drifts up a point a year, lab fees nobody has renegotiated since the practice opened: none of these announce themselves. They show up as a year-end surprise from the accountant.
This is the numbers curriculum. What to measure every week, what good looks like, where the money leaks and the order to plug the leaks in. If you only read one hub on this site, read this one.