Youtube player size changes on different screens (2 monitor setup)

Hello.

I have noticed that every time I move my browser to second screen when it is playing YT the size of player changes. I checked it on Chrome and IE browsers and the effect is the same. Below I am putting link to the screen shot.
Imgur: The magic of the Internet

As you can see the white stripes on the sides (right part of the screenshot) are much smaller than the ones on the left part. Both players are set to default but the issue is also present in the cinema mode of YT.

I tried swaping the monitor configuration in Windows - change the left screen from main to additional one but this results in YT changing size accordingly.

Is this normal behaviour for YT/Windows to change size of the player when browser is put on additional display instead of main one? Or maybe there is some option that could be change?

Much obliged for any help

is it everything that is full windows when you drag to other screen gets put at a smaller size. I know when I move a browser screen over to the other it doesn't keep same size have to maximize it.