Operator and Minimum visit value attribute define the relative visit total a guest must reach to be included in this Average visit segment. Also, this depends on the average factor that is being used in the segment and the duration on which the segment has been created.
For example, when you set "Minimum Visit value" to "More than or equal to 2" and Average factor to "60 days", it will include all those guests who have done at least 2 visits in the segment's duration, and their average visits will be determined accordingly.