According to its flavour text, the Wind-Up Nanamo was created to celebrate Nanamo's tenth anniversary as Sultana, and she was crowned at 15. That would now make her 25.
However, according to the Tales from the Calamity, Nanamo was 16 during the Calamity, which would now make her 21/22.
Am I missing some math or is there a mistake in either text?
Also, who is the poor kid who had to rule Ul'dah at an even younger age?!