No spin number you are shown deserves much trust

Broadcast tracking gives you revolutions per minute to three significant figures, and the measurement underneath it is nothing like that precise.

Ball tracking systems are extremely good at position. Multiple calibrated cameras, a ball with known dimensions, a well-understood trajectory model: where the ball landed is close to solved, and line calling moved to cameras for exactly that reason.

Rotation is a much harder problem, and the numbers presented alongside it are not produced the same way.

To measure spin directly you would need to see the ball's surface markings rotate, which at professional speeds and normal broadcast frame rates you cannot. So spin is generally inferred: you fit the observed flight path against an aerodynamic model, and whatever rotation would produce that curvature is reported as the spin. Which means the number depends on assumptions about drag, air density, the ball's condition and the model itself, and every one of those assumptions is approximate.

Change the ball, change the altitude, change the humidity, and you change the inferred number without changing what the player did.

I am not saying the figures are invented. Directionally they are informative; a heavy topspin forehand really does read higher than a flat one, and comparisons within a single match on a single court are reasonably safe. What is not safe is the thing broadcasters and social media accounts do constantly, which is comparing a figure from one tournament against a figure from another, several years apart, on different equipment, and drawing conclusions about who hits the heaviest ball in history.

That comparison is doing precision it has not earned.

There is a second problem, which is selection. The spin figure you are shown is almost never a match average. It is the standout shot, chosen because it was extreme, from a rally the producer liked. A maximum drawn from a few hundred samples is not a description of a player's game and it is presented as if it were.

What I would actually want, and what no broadcaster shows, is distribution. Give me the spread of a player's forehand spin across a set and I can see whether they vary, whether they flatten out on short balls, whether they collapse into defensive margin under pressure. That is a picture of somebody's tennis brain.

A single big number is a picture of nothing, and it takes up the same amount of screen.