Every figure in Ifa is written the same way: eight positions in two columns of four, read as a pair rather than as a single run of eight. Each position is either one stroke or two. That is the entire notation, and it is what makes the corpus countable. Sixteen patterns exist for a column of four, so sixteen figures exist in which the two columns are identical, and those sixteen are the principal odu, distinguished in speech by the word Meji, meaning two or doubled. Oyeku Meji is the second of them in the sequence as ordinarily published.
The pairing is not decorative. A figure whose columns differ is a distinct sign with its own name, formed from the names of the two halves, and there are two hundred forty of those. Together with the sixteen matched figures they make the two hundred fifty six odu that the corpus is actually organised around. A diviner is expected to hold material for all of them, which is why the sixteen are taught first and why the ordering of the sixteen matters to instruction.
Oyeku Meji and Eji Ogbe are the two extremes of the notation, one figure carrying a double stroke in every position and the other a single stroke in every position, so the pair is often introduced together when the notation is explained.
The verses attached to Oyeku Meji, and what a diviner does on casting it, are part of an initiatory transmission and are not given here.