Its Alexes way of recording the Hex. The Stems are roman letters, so I is Jia and the relations are the K, P and the other stuff.
Another way to know its Alex is that there is no other way of calculating void that I'm aware of, where the void can end on Jia day(as the void when calculating traditionally always start on jia day and end after gui days).
Yet he calculates it differently as well, suggesting that the person that read that was using his notations and his point of view of when void ends, yet the branches that are in void would be different if the Jia/Wu was calculated traditionally(they would be wu and wei if calculated by his methods).
It may actually be example from his website, I'm still following the advice of avoiding it, so I haven't read most of the stuff there, just the conversion so I can make the Super I Ching notation, as members wanted that initially(in the app). If it is example from his website, he is using traditional method for calculating the void, instead of his own method, yet he is using his own method for determining when that same void will end. And that seems silly....