It’s perfect! I think most of the readers prefer 10-15 min because it is not too long, but then again it isn’t too short either. For example I don’t really like 5 min chapters because I feel like I am kinda “wasting” passes if that makes sense, I am not saying short-chaptered stories can’t be good, but I would always rather give a chance to the story with longer ones. But then again stories with more than 20 min chapters are just too long and it can become too much very quickly to the point where I am just wishing for it to end already. So I think that your choice of going with 10-15 minutes is excellent 
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