User Meta Update on user save hook wordpress customer meta update.

User meta update.

// function user_role_update($user_id, $new_role)
function client_number_update($user_id){
    if(isset($_POST['customer_client_number'])){    
        update_user_meta( $user_id, 'client_number', $_POST['customer_client_number']);
    }
}
add_action('profile_update','client_number_update');