javascript - How can I understand the "asyncTime" in TodoMVC benchmark test? -

i wanted performance benckmark test among javascript framework , other frameworks.and found "todomvc" benchmark test.a lot of people use result of test.it seems reasonable.but can't understand "asynctime" of test.

var starttime = now(); testfunction(preparereturnvalue, contentwindow, contentdocument); var endtime = now(); var synctime = endtime - starttime;  var starttime = now(); settimeout(function () {     settimeout(function () {         var endtime = now();         callback(synctime, endtime - starttime);     }, 0) }, 0); 

this code snippet "synctime" , "asynctime".

why use 2 "settimeout" "asynctime"?

dose make sense?

this original repository. https://github.com/matt-esch/mercury-perf