Is media duplication normal?

Question

Sass

Media is duplicated when exiting main.css , what should I do about it? does everyone have it? example below:

media (min-width: 768px) and (max-width: 991px) {
body .header {
font-size: 30px;
}
body .box {
font-size: 10px;
}
}

media (min-width: 768px) and (max-width: 991px) {
body .sidebar {
font-size: 10px;
}
}