That is definitely a 10 round mag pictured with the gun. The standard cap mags for the 15-22 are 25 rounds though.Can't say for certain, but they appear to be auctioning a non-legal in NY firearm.
The ad says "Under the NYS Safe Act, this rifle is not considered an assault rifle and is a legal firearm", buuuuut...
It COULD be a fixed magazine (though it does not immediately have the appearace of such), but then it says also , "the ammo capacity is 25 rounds". So...