What is the meaning of the aspect ratio of the mobile screen 330 500?

  node.js, question

var $win = $(window),

$doc = $(document),
 sizebr = 330 / 500;
//initialization
 $win.on("load resize", init);
 
 //initialization
 function init() {
 var winH = $win.height(),
 winW = $win.width(),
 winSizebr = winW / winH,
 $page = $(".page");
 
 //For MEIZU and other special proportions
 if (winSizebr > sizebr) {
 $page.each(function(i) {
 $(this).addClass("meizuSize");
 });
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Sizebr = 330/500; What parameters are 330 and 500? ? Is there any detailed explanation?

I guess it is a low-resolution device fitting ntsc480 line resolution 720×480, only 500 wide