unity – Main Camera re-sizing in 2d

My UI :

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An UI from YouTube video :

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Look my camera’s size is 10 and his camera’s size is only 5. But, my camera’s width is larger than height. If you look at scale (x,y,z)=(1,1,1). I tried to change them. But, nothing changes.I tried to change ViewPort Rect then, I am able to change the size of Main Camera. But, look at following image. His ViewPort Rect is 1 by 1 mine also. But, we have differences of width and height.

How to fix it?

enter image description here