ROBLOX Studio Mouse.X and Mouse.Y offset in non-standard behavior

[Quenty]

When hovering right below the black bar, the mouse.X and mouse.Y read to ignore the offset created by the topbar. This is nonstandard behavior and is not replicated in-game.

However, once you click, the mouse X and mouse Y will revert to standard behavior. As soon as you move the mouse again, it stops.

An example of the nonstandard behavior, where mouse.Y is ignoring the top-bar offset

This only happens in studio, and is inconsistent with what happens online.

[Quenty]

Silent137 said on the developer forum

This is certainly an unusual behavior, and I agree, one of them is probably wrong!