Actual date calculation for original durations

I must have a setting configured wrong when I installed P6 8.3. When an activity is over 2 days or more the calculation in the actual is always one day short. When it should be 3 it is 2 in the actual when it should be 5 it is 4 and on and on. I cannot have an activity start and finish on the same day. I must have at least one calendar day in between or I get and error message regarding that the end date cannot be before the start date. I am using a 7 day a