What’s the purpose of the Negative margins here [in main.css] ??

.region.fullscreen {
position: absolute;
top: calc(-1 * var(–gap-body-top));
left: calc(-1 * var(–gap-body-left));
right: calc(-1 * var(–gap-body-right));
bottom: calc(-1 * var(–gap-body-bottom));
pointer-events: none;
}