Just checked Solana Beach in the MLS. When I run stats which I know is low, I get 85. When I run all the listings which I know is accurate I get 92. I purposely selected places with less than 250 because the system caps out at returning 250 listings. ZIP has 100. Thats a 10% difference.

Santee
Stats 216
MLS LIstings 227
ZIP 234

I could keep going but I think the truth is probably somewhere around halfway between the numbers I get running stats and what ZIP posts.