Peak occupancy considering shifts

Hello, We are calculating the occupancy in a project that works with shifts. The 1st shift works from 7:00 to 3:00 pm, 2n shift from 3:00 pm to 11:00 pm and the 3rd shift works from 11:00 pm to 7:00 am. In the PI form I used the non-standard occupancy patterns option in which I have to provide the manual calculation for the peak occupancy and it specifies that I have to consider shift overlaps. Does this overlap refer to overlapped working hours? or should I consider in this calculation the peak volume shift + the next shift even if there´s no overlapped schedule? Thank you in advance. Regards!