Its actually really small, mostly because bigger networks take longer to evaluate which slows down the search making it shallower and ending in a less clever algorithm.
It's just over 82,000 parameters.[1] That's a very shallow, small NN - by comparison something like EfficientNet-B1[2] is 7.8M parameters, and that's considered a small network.
[1] https://www.chessprogramming.org/Stockfish_NNUE#NNUE_Structu...