Hello! I'm doing a brief presentation on plainchant for a youth choir I accompany. They're working on Britten's Ceremony of Carols so I plan to show them the chant notation for Hodie Christus natus est. I'm newer to chant myself, so trying to anticipate their questions and have answers at the ready. I'm sure they will ask about EUOUAE at the end of the chant. Based on this forum thread, my understanding is that one matches the EUOUAE tones to "saeculorum amen" in the linked PDF; however, none seem to match, so maybe I'm understanding incorrectly. Could someone point me in the right direction? Thank you in advance!