Scale image isn't scaling my image

[Lost Birds]

My canvas is sized 1920x1080. The picture I'm working with is 1920x1279 and I'm trying to crop one part of it so I get 1920x1080. When I press Shift+C and enter size I want to crop it to, the cropping outline is much smaller than the size I'm entering. I know this for a fact because as I've said my canvas is 1920x1080 but when I put crop size into the same resolution (1920x1080), the crop outline is smaller than the canvas.

How do I solve this? I can't formulate the question good enough to find a solution via google, hence I'm asking here.

Example: gyazo screenshot