There is no way to earn extra Cinthia quests, only Wizard quests. I asked a UA to check your logs, and it looks like you only did 15 Cinthia quests, but the 15th quest got counted twice towards your quest total. This glitch does not normally occur, and was likely related to server updates we were doing yesterday.

In the past when quests have double-counted, we have been fine just letting it slide, so no worries about the extra quest tally, and thanks for reaching out. :)