They aren’t setting those numbers, that’s just echoing the values stored in the controller.
This is how LightBurn knows the maximum:
Typing manual S values would require you to be in the correct mode. You’d need to type G1 with a feed rate first, like G1 F100, and then you can use M3 and set an S value. If you aren’t in G1 mode, the S values are ignored because the “spindle” isn’t running during G0 moves, only G1.