Days Total represents the number of days in the selected month that are available for a staff member to work. This is calculated from the individually customisable Capacity Settings for Users. 

Days Planned is the number of days allocated to tasks for the selected user. This takes into account all remaining effort on all allocated tasks (not including completed tasks) for the month, divided by the staff member's expected productive days and productivity levels based on their Capacity Settings.

Days Free is an estimation of how many days are available for the selected staff member to be allocated additional tasks.

Days Completed is calculated by dividing total hours in timesheets entered by a staff member by expected hours per day.

Days Incomplete is the deficit between Days Completed and the number of days that have passed.

Days Over Capacity is an estimation of how many days work are scheduled over what could be expected given the staff member's Capacity Settings.

The diagram below shows how the capacity is calculated & displayed.