Photos Plan focal point

When planning a Photos Plan mission, is the focal point altitude setting relative to the take off altitude? In other words if I set it to 0 but takeoff from a point 100 ft higher than my POI where will the camera focus?

And also maybe how come I cannot find this information in the help documentation?

The focal point altitude is in relation to the flight altitude. The difference in those elevations and the distance from the camera calculates the pitch of the gimbal.