Header image size

I struggle a bit with header image size. According to documentation the size should be 1000 × 250 pixels, WordPress admin panel shows 1920 × 1080 and automatically crops down to that size. It looks well on mobile but on larger screens the picture occupies most of the vertical space it also seems higher height then on demo pages I have seen. I am pretty sure I am missing something, but I can’t find what it is?

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