It could be due to browser caching. Try force-reloading the browser tab when you are about to download the plugin.
The version number appears twice. First, in the plugin header (as seen in your screenshot) but this info is only for you to read it in the plugin manager. Second, the version number also appears just below the plugin header:
var Imported = Imported || { };
Imported.MK_UICustomizer = '2.1.1';
This is where the code actually reads the current version number.