The docs say the Asus GL502VT can have a max of 16GB RAM. However, I just put in a 16GB stick (there’s one slot, from the factory populated with a 4GB stick; just swap it out). Added to the 8GB soldered into the motherboard, you can get up to 24GB.
Figured I’d add a marginal bit of data to the body of knowledge on this laptop 😉