Fair enough. I erred low due to many sites restricting symbols. Also considered leaving out symbols entirely and going with 62 for that reason. Fewer possible symbols just means extra characters, and probably doesn't even have a huge impact on that number. Nine alphanumerics (62 possibilities) beats eight characters with 95 possible values, and if you want something easy to type manually, could be preferable. Depends on usage and site requirements.
The norm is 95 values. That's the all ASCII printable characters, or just count them on your keyboard.
(I'm not sure if that includes the <space> character.)