Cyrillic has a letter for the same sequence, and the atlas pairs the two. Neither carries a numeral value, since Greek had nothing to supply here and the Glagolitic count had stopped several letters earlier.
The pairing is instructive because it holds in the part of the alphabet where the two scripts had least reason to agree. Nothing in the Greek model dictated that either alphabet should have a single letter for a glide plus a nasal vowel. Both do. Both put it in roughly the same place in the order. Both give it a name that no one can explain. That is a considerable amount of agreement about a sign that neither script inherited from anywhere, and it is one of the reasons the two alphabets are treated as belonging to one tradition even by scholars who disagree entirely about which came first.
The atlas records the pairing as a correspondence of sound, position and name, and declines to state a direction. The relations from these letters that concern descent are marked debated and carry the competing explanations, so a reader sees what is agreed and what is argued in the same place rather than being handed a conclusion the evidence does not support.
The sequence itself did not survive. The nasal vowels were lost everywhere except Polish, and the glide before them was absorbed or lost with them, so the sound this pair of letters records has to be reconstructed rather than heard anywhere today.