How CanvasSize works?

I am kinda confused – how CanvasSize property works?

At first I thought that CanvasSize is how much of space I want in total compared with ScrollingFrame itself. And it logic worked for me – I was making AutoScale and it seemed to work fine?.. Now I am confused: I set CanvasSize to {0, 0}, {0.7, 0} and I can scroll. So I thought that maybe CanvasSize is how much space is added to the size of ScrollingFrame.

But after a simple test this logic also was broken: I have a ScrollingFrame with AbsoluteSize (…, 147.693)

When I set CanvasSize to CanvasSize to {0, 0}, {1, 0} and scroll to the bottom, CanvasPosition would be 147.693. But when I set it to {0, 0}, {2, 0} it would be 443.079, which is 147.693 * 3, not 2. Now my logic is broken.