add_action( 'wp_login', function( $user_login, $user ) {

    if ( ! did_action( 'wpf_user_created' ) ) { // only if the user wasn't just registered and auto-logged in.
        wp_fusion()->user->user_register( $user->ID );
    } else {

        $data = array(
            'last_active' => 'X';
        );

        wp_fusion()->user->push_user_meta( $user_id, $data );

    }

}, 10, 2 );

add_filter( 'wpf_user_register', function( $user_meta, $user_id ) {

    $extra_data = array(
        'last_active' => 'X',
        'user_id'     => $user_id,
        // lastname, firstname, and email are already synced by default, you don't need it;
    );

    $user_meta = array_merge( $user_meta, $extra_data );

    return $user_meta;

}, 10, 2 );