Here's what was said :
Tony: Will you be doing a full 24 episodes or how many total will you be doing this year?
Damian: We did another 13, which at the time was all we could do because our vis effects pipeline is so tight getting into a 20 order Season 2 would be very, very hard. I think that if we go for 13 there is a possibility of a larger order but that is all speculative right now so
By the way, if you like sci-fi in general then you should check out Tony's podcasts as he has some very interesting guests and covers a wide variety of subjects.
Source : Sci-Fi Talk