Set version number in child’s style.css file

you can define the version when enqueuing the file :

add_action("wp_enqueue_scripts", function () {

    wp_enqueue_style(
          "child-style"
        , get_stylesheet_uri() // = get_stylesheet_directory_uri() . "/style.css"
        , ["parent-style"]
        , wp_get_theme()->version // use the child theme version
    );


});