First time out, couple questions

[Hawkeye]

Hey all,
I got my bike out today to do some pre-ride maintenance, and I have a couple questions.
First a little background. The bike I bought is an 03. The guy I bought it off of (for some reason) was running it with the choke closed(?) and the throttle screw played all the way out to lower the idle.
Because I bought it end of Dec, I parked it in my friend's garage and it's been sitting until today.
Today I did a full oil change with filter, charged the battery, started it up and adjusted the throttle screw.
My first issue: I think I *might* have over filled the oil, I'm not entirely sure. When the bike is running, it sits at the full mark, but when I turn it off, it fills the whole "window." I haven't noticed any issues, but I'm wondering if there's a way to rectify it without pulling the drain plug.
Second issue: There is what appears to be a slight backfire when I let off the throttle while it's in neutral. There doesn't seem to be any performance issues that I can tell, and you can only barely hear it when sitting in place revving the engine a little.

I know that's a lot of typing, but anyone who reads all of it and has a suggestion or two, I appreciate all help.
Thanks,