contentiskey on "Line spacing for h1, h2, etc."

I used "inspect element" (a chrome development tool) and found:

an example of an H1 tag with both top and bottom margin

@media screen and (min-width: 77.5em)

.entry-content h1, .entry-summary h1, .page-content h1, .comment-content h1 { font-size: 39px; font-size: 3.9rem; line-height: 1.2308; margin-top: 1.641em; margin-bottom: 0.8205em;
}

an example of an H3 tag with both top and bottom margin

@media screen and (min-width: 77.5em)
.entry-content h3, .entry-summary h3, .page-content h3, .comment-content h3 { font-size: 27px; font-size: 2.7rem; line-height: 1.1852; margin-top: 2.3704em; margin-bottom: 1.1852em;
}