I believe this is the same bug that has been reported before, at least back to July, if not earlier. Here is
one thread that also describes the issue. In my case this morning, I have (2) items showing under 'Due Soon' in the Home screen and a badge count of (2). However, clicking on Contexts from the Home screen shows a total of (4) items due soon as two of the four will not be available until later today. Setting the Context preference to Remaining will display everything, but I find setting the preference to Available to be much more useful on the iPhone.