Sorry for my poor English but let me ask some question.
I bought the Theme which is named “METRIC”(http://themes.grandpixels.com/metric/)
And I want change height of Divs but I don’t have idea how can realize it.
ex) I want change heights of parts of “header”, “callout” and so on.(obviously, they are names which are being used in this theme…)
I have been looking for these parts in style.css, but I couldn’t have understand it well.
I suggest you contact the author of the theme here.
Ask them how it would be possible to change the height of the header.
(I see that the author does not provide support for the theme but it can be worth a shot to try asking them.)
Other than that, authors usually provide a Themes Option panel. Here you can change the many options in the theme including the height of Header.