I doubt your ignorance is any more than mine.
I should have provided a link to that pic and info on Khufus Horus name, im surprised Mr Stower didn't jump on me and demand i get permission to post it.
So yea its my fault for not providing this info, so yea, Khufus Horus name, my information came entirely from Wikipedia, of course there information is constantly subject to updates and correction, so take it at face value i guess.
A clip from their page on Khufu.
Length of reign
It is still unclear how long Khufu ruled over Egypt, because historically later documents contradict each other and contemporary sources are scarce. The Royal Canon of Turin from 19th dynasty however, gives 23 years of rulership for Khufu. The ancient historian Herodotus gives 50 years and the ancient historian Manetho even credits him 63 years of reign. These figures are now considered an exaggeration or a misinterpretation of antiquated sources