Quick hack to find the number of videos and average length in one of the lessons on learn.cantrill.io. Will probably also work on other teachable platforms, but that's where this was originally written for.

cantrill_stats.js

function conv(time){
  let s = time.split(':');
  return parseInt(s[0]) + (parseInt(s[1])/60);
} 

let names = document.getElementsByClassName("lecture-name"); 
let total_time = 0
let videos = 0
const re = /\d+:\d\d/

for (var i=0; i < names.length; i++){
  let t = names[i].innerText.match(re); 
  if (t !== null){
    time = conv(t[0])
    videos += 1
    total_time += time
}}
total_time / videos