I was reading Foundations of Astronomy by M Seeds and was wondering about the precession of Mercury. There he says it is 43''/century or about 29 km per revolution past the position predicted by Newton’s laws or in total 12,000 km — more than twice its own diameter per century.
Mercury's angular diameter is between 4.5″ – 13.0″ depending on the positions of Earth and Mercury at a particular moment so 43''/4.5'' = 9.5 and 43''/13'' = 3.3
The angular diameter shift observed would be between 3.3 and 9.5 times Mercury's diameter but 12000 km / 4880km (Mercury's diamater) would result in a 2.45 diameters shift.
Do you know what information I am missing here?