Looks like it's idling fine to me. But it's always a good idea to monkey around with the idle mixture on a new bike until you're happy with it imo. 2 and a half turns out on both of the screws should be okay though, if you don't want to do that.
A lot of people think this is common sense, but it wasn't to me the first time; don't get cleaner on any rubber parts, especially the diaphragms. A little bit on the hoses is nbd, just wipe it off, but do not get any on the diaphragms, and place them somewhere like in a zippy bag when you set them aside so you won't get any crap on them. I'm assuming you've seen these already, and they are for the pre-2008 Ninja 250's, but I'll put 'em here for good measure, as most carburetors are generally the same in design.
Cleaning:
http://faq.ninja250.org/wiki/Cleaning_the_carbs_1
http://faq.ninja250.org/wiki/Cleaning_the_carbs_2
Syncing:
http://faq.ninja250.org/wiki/How_do_...carburetors%3F
Adjusting the idle:
http://faq.ninja250.org/wiki/How_do_...dle_mixture%3F
EDIT: Others are recommending you don't touch it. I'm a kinsesthetic learner. If you're afraid you'll mess something up, don't do it, but if you're going to mess with the idle and clean the carbs eventually (protip: you will), you might as well do it now since all the knowledge is fresh in your brain. But I'm still reasonably new, and if @
Motofool has something to say that opposes it, I'd take his advice over mine; the guy's very smart and wise
