View mode and full hd

Hi all.
Sorry if it has been answered before, I've been searching for this but haven't found.

In a 1080p video, if I choose video Options - Video settings - View mode - Original size, image is very small to be a 1080p.
If I choose the same in a 1080i, it shows the correct size.
They are supposed to be the same size, why are they different in screen?
This is 1080i, http://pastebin.com/X5yHRvXa and this is 1080p http://pastebin.com/b9zukTBT

Thanks in advance?