Chuen is the Yucatec name and B'atz' the K'iche', both meaning monkey, and the eleventh sign is the one on which the two traditions diverge most consequentially in practice rather than in meaning. In highland Guatemala the count is conventionally described as beginning from B'atz', and the day 8 B'atz' is when new ajq'ijab' complete their training, so the sign occupies a position in living K'iche' practice that no Yucatec source anticipates.
Central Mexico places Ozomatli, monkey, in eleventh position, agreeing with both Maya names. The monkey in Mesoamerican thought is the patron of writing, of music and of the arts, and the Popol Vuh tells of the elder brothers of the Hero Twins being turned into monkeys and afterwards invoked by artists and scribes.
That the 260-day count has no arithmetical beginning is worth restating here: 260 days form a closed loop, and any position can serve as a conventional first day. Yucatec sources start from Imix, highland practice speaks from B'atz', and neither is more correct than the other. Chuen is not a Year Bearer in the Classic set, Ik, Manik, Eb and Kaban, nor in the Yucatec set, Kan, Muluc, Ix and Kawak.
The eleventh position therefore carries a caution for readers of this atlas. Numbering the signs from Imix, as the atlas does, follows the colonial Yucatec ordering and is a presentational choice, not a claim that the count starts there. A highland daykeeper reading the same twenty would begin the list at B'atz' and arrive at exactly the same cycle, since a loop has no first element until someone names one.