Hi,
bloginfo('stylesheet_url') will return theme's stylesheet path like
http://example.com/wp-content/themes/YOUR_ACTIVE_THEME/style.css
But everytime you are getting the filemtime(file modified time) of style.min.css file. Instead of this you should write the following code:
<link rel="stylesheet" type="text/css" href="<?php bloginfo('stylesheet_url'); echo '?ver=' . filemtime( get_stylesheet_directory() . '/style.css'); ?>" media="screen" />
Now it must work when you modify your style.css file.
Hope this will work for you!