Employee sicknesses will only be added to their Total Days value once the sickness has been closed.
If the sickness has the status Open and is missing an end date, this will not be added to the total number of days displayed in the Total Days field.
To view the Total Absences stats:
Search for the employee and go to their profile.
Click Absence, then Sickness.
The stats will be displayed on the right. As you can see in the screenshot below, although the employee has 7 days of sickness, because the sickness is still Open this will not show in the stats area.
Once the sickness is closed, the number of days will be added to the Total Days value.