So Faelins are weird, and one of the ways that they're weird is the fact that for the majority of their lives, they grow in a fairly linear rate, they grow the fastest during the first 10-12 years and then settle into something a little slower where they double in size every 50 years or so. Faeins are biologically immortal, meaning they typically only die to outside causes like a larger Faelin deciding they'd look better aliven't or a determined human with a high caliber rifle; there isn't actually an upper size limit on how big a Faelin can grow as long as they have the space, time, and resources to do so.

What we're actually seeing here is Serivas being noticed by their much older Chimer parent, Yivern, in some huge cave or something; Yivern is the largest of Seri's parents (but not the oldest because Melrent is ancient and just got locked up for a few millennia). And fun fact: it's hard to see in this lighting, but Seri inherited their topscales color from Yivern, they're both red-orange idiots.

And as for the stats, this mistake of a drawing took 2 hours and 43 minutes according to Krita