add offset to post category

snippet.php

add_action( 'pre_get_posts', 'lit_offset_category_filter' );
function lit_offset_category_filter($query) {

    if ( ! is_admin() && $query->is_main_query() ) {   // Apply to main WP query
        if( $query->is_category()) {                   // Only on category pages

            $offset = '3';                             // Number of posts to offset

            $query->set( 'offset', $offset );

        }
    }

}