It’s not super clear by ASUS’s documentation, but this is not limited to a 256GB M2 SSD. It was available from ASUS with either a 256GB or a 512GB M2 SSD. Then again, their documentation also says a maximum of 16GB of RAM. Buyer beware that the specs may not be accurate.
Ref: Mini PC PN62S - Tech Specs｜Mini PCs｜ASUS USA
Still not clear from the description (at least to me) if it comes with storage + ram. It feels like for the $370 you get “barebone cpu + mobo + case/psu” without storage or ram. Is that accurate? Should have a description with like “add your own ram up to X and storage in configuration of Y”