add note that memory is 1024 based

src/js/index.js

@@ -281,9 +281,9 @@ app.filter('prettyDomains', function () {
     };
 });
 
+// we use 1024 unit in memory limit in manifest
 app.filter('prettyMemory', function () {
     return function (memory) {
-        // Adjust the default memory limit if it changes
         return memory ? Math.floor(memory / 1024 / 1024) : 256;
     };
 });