JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="alphaList">
    <li>1 - 5 days</li>
    <li>11 - 15 days</li>
    <li>16 - 20 days</li>
    <li>6 - 10 days</li>
</ul>

JavaScript

var items = $('ul li').get();
items.sort(function(a,b){
  var strA = $(a).text().split(' ');
  var strB = $(b).text().split(' ');

  if (parseInt(strA[0]) < parseInt(strB[0])) return -1;
  if (parseInt(strA[0]) > parseInt(strB[0])) return 1;
  return 0;
});
var ul = $('ul');
$.each(items, function(i, li){
  ul.append(li);
});