Where to edit this CSS

Hi:
I'm seeing this CSS being generated inline on all pages of my site:

.entry-content .alignwide, body:not(.no-sidebar) .entry-content .alignfull {
    margin-left: -40px;
    width: calc(100% + 80px);
    max-width: calc(100% + 80px);
}

I'm pretty sure it's generated by GeneratePress, as its one of the selectors in the following inline CSS:

<style id='generate-style-inline-css'>
body{background.....

My question is, where in the Customizer can I customize the rules for `.entry-content .alignwide and so on? I'd like to remove the "margin-left: -40px" part, as it's wrecking havoc with my design.

Thanks!