The preview tab is just that... a place to preview what the macro looks like as written by ISBoxer for World of Warcraft; and unless you're using macro variables then the preview tab is going to show you the exact same thing as you've entered on the main tab.

If an in-game /reload didn't fix the issue, then you must still be doing something wrong. You can either share your profile, or watch the video on this page which shows exactly how to go about using macros with ISBoxer.