Trouble finding padding settings for .page-header

Hi - I'm trying to change the padding on the .page-header element on the archive template. Specifically, it's the .page-header element that's generated in the generate_archive_title() function.

I can see that in <style> in the head, padding is set to 20px 20px 20px 20px, via this rule:

.separate-containers .page-header {20px 20px 20px 20px}

The fact that it's in <style> leads me to believe it must be a Customiser setting.

Problem is, I can't find where the setting is. In Customiser > Layout > Page Header, there are no padding controls.

Sure I can just use CSS to override it manually. But I'd like to use Customiser if the setting is there.

Thanks for your help.