Sometimes the calculated total time reserve is so small that the task can also be considered critical. For example, if the task’s reserve is 1 day, while task durations are estimated in weeks. In 1 day, it is unlikely that you can make an effective decision to avoid missing deadlines. And a seemingly non-critical task can easily become critical.
A good project manager assesses not only the critical but also the “near-critical” path. In MS Project, there is a good setting for analyzing the “near-critical” path.
In the File - Options window on the Advanced tab, you should scroll down to the very bottom of the tab and indicate in the field Consider tasks with a reserve of no more than … days as critical - the necessary value. Then click OK.