Broadcast Theme : Mobile Home Page Container

Hello

i`m using broadcast Theme ,for mobile view, change margin size container left & right to 20px only work for blog containeronly . not work for container box homepage ,and box container at homepage not center for mobile view
can help me

@media (max-width: 768px) {
    body .site.grid-container {
        margin-left: 20px;
        margin-right: 20px;
    }
}

tq