By default, Minitab displays all missing values in your tables, but does not include them in calculations unless you check Include displayed missing values in calculations in the Options sub-dialog box. When a data point is missing, by default, the entire worksheet row (observation) is omitted from the calculation. You have to decide which statistic is more meaningful for your application. If any part of the data for an individual is missing, some researchers would eliminate the entire point from the study, while others would use the data they can.
In this example, for Stat > Tables > Descriptive Statistics, you are missing eye color data for 1 female and 2 males.