I think there are too many traditional archers out there who are trying to imitate the dentist. They regurgitate information without the complete understanding the dentist has. And even the dentist works within a very narrow view exhibiting tunnel vision in many cases. I think in that one particular phrase this writer simply forgot to cut and past the whole equation. Seems to make mathematical sense if he had put it in terms of "every ten yards" or "every ten meters". That would be very dang close! Honest mistake I would assume.
My usual instincts after reading way too many of these copy cat articles, since the dentist got popular, is to ignore anything that tries to correlate Ke to penetration. The dentist has been the only one to ever present a case with a solid foundation. And even then, as mentioned, his writings have been quite close minded and incomplete in many areas.
Ashby is a good read though. Just readers should beware the focus in narrow and riddled with traditional bias. And, as he states many of the things people love to concentrate on in his writings he has listed quite low on his scale of importance. In his defense he has not tried to hide this! It just seems his #8 thru 10 seem to be the things everyone wants to talk about

That is not really his fault!
Claiming to be the first to ever do the African studies when Savora did similar studies years prior in conjunction with the Rhodesian government...well yeah! That is his fault

Oddly enough the Rhodesian government concluded those devices the dentist has become famous for should be outlawed for use in African game hunting. It took Savora and one of the Wardens
(I forget his name right now) quite a bit of effort to explain you really can not accept one without the other. Their efforts are the only reason the dentist was ever allowed to do what he did years later. Yet the dentist attempts to take all the credit.