GradeCalcCorrector - correctly calcs grade on full report page. Not flexible, may contain errors.

gradecalccorrector.user.js

// ==UserScript==
// @name         GradeCalcCorrector
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Correctly calcs grade on full report page. Not flexible, may contain errors.
// @author       You
// @match        https://e.sfu-kras.ru/grade/report/user/index.php?id=*
// @grant        none
// ==/UserScript==

(function() {
    'use strict';
    function calc_right(doc) {
        return Array.from(doc.querySelectorAll(".levelodd[headers~=grade]")).map(v=>~~v.textContent).reduce((acc,v)=>acc+v,0);
    }

    let fgrade = calc_right(document);
    document.querySelector("h2").after(`Суммарная оценка: ${fgrade} балл(а)`);
})();