What is centre of box?
Centre of Box predicts are used to point ground antennas at the satellites in orbit. Because the satellite's orbit is never perfect, the latitude and longitude vary with time. By peaking non-tracking earth station antennas to the Centre of Box, antenna gain variations are minimized.
Each day, there are two points where the satellite comes closest to the centre of the station keeping box. These points are given in the Centre of Box predict table that pops up when you click on a satellite. In the table, the Latitude Deviation is the deviation from the nominal station keeping longitude, and the Longitude Deviation is the deviation from the nominal station keeping longitude. The smaller the deviation values, the closer the satellite is to the Centre of Box.
Not all Centre of Box approaches are equally close. When peaking large antennas it is advisable to look for a Centre of Box approach with minimal deviation.