What is Get Mouse X/Y based on?

Using the Get Mouse X/Y functions in a blueprint gives you some kind of mouse position delta value, but what exactly is this value? The description just says “Return the current value of input axis key Mouse X” which isn’t particularly helpful in this case.

I first assumed it was how far the mouse had moved since last frame (in pixels) or something similar, but after some testing that is quite obviously not the case, or at least it’s not in pixels. It’s certainly something similar to this, is it maybe in a different format than I expected? Where exactly does the value come from?

Thanks!

When mouse is visible.

You testing it when mouse is visible or when mouse rotates character camera?

sorry to necro, but I would also like to know