It isn't an exact number, the Moon and Sun also cause perturbations, along with optimizing the sensor/antenna foot print of the service area.

European Space Agency (ESA) “Requirements on Space Debris Mitigation for ESA Projects” Operational Requirements (OR) state in OR-3 ( https://conference.sdo.esoc.esa.int/proceedings/sdc7/paper/864/SDC7-paper864.pdf ):

"OR-03. Where practicable and economically feasible, space systems outside the low Earth orbit (LEO) and GEO protected regions shall implement means of end-of-life orbit disposal to avoid long-term interference with

operational orbit regions, such as the Galileo orbit. The geosynchronous protected region (GEO region) is a segment of a spherical shell defined by:

- lower altitude boundary = geostationary altitude minus 200 km,

- upper altitude boundary = geostationary altitude plus 200 km,

- latitude sector: 15 degrees South ≤ latitude ≤ 15 degrees North,

- geostationary altitude GEO h = 35786 km

The correct height of the orbit of a geostationary satellite is approximately 35,786 kilometers (22,236 miles) above the Earth's equator. At this height, the satellite orbits the Earth at the same rate as the Earth's rotation, allowing it to appear stationary relative to a fixed point on the Earth's surface. This specific orbit enables geostationary satellites to provide continuous coverage of a particular area on the Earth's surface, making them ideal for applications such as telecommunications, weather monitoring, and broadcasting.