My advice would be to use an HTML list, like this:
let htmlString = Quarter.reduce((accum, current) => accum += `<li>${current}</li>`, "<ul>");
htmlString += "</ul>"
this.Quart.innerHTML = 'RESULTS: '+htmlString;
For older versions of JS you could do:
var htmlString = Quarter.reduce(function(accum, current){ accum += "<li>"+current+"</li>"}, "<ul>");
htmlString += "</ul>";
You can style the list separately to your liking.