My forum has currently over 61,000+ posts and the 48 hour stats is as so... http://screencast.com/t/GtbncKd72z5t Is that a lot or very low?
It's reasonable. I'm guessing green username means they're a user and any other colour they're a staff member? If so, you have way too many staff. Cut down a bit on that.
How long has your forum been operating? That's a small amount of members logging in unless it is only a few months old or less, then it's not bad at all. How large are you aiming to make it? Whether the size it is is "good" depends on what you want your forum to be size wise.