Apparently the ship is clean in the jurisdiction where you scanned it. If you shoot it you will become wanted in that jurisdiction yourself. If the total bounty is high it might be worth it though. Probably better to follow the ship and attack it when it jumps into an anarchy system (there's a small chance it jumps into a system where it is wanted).
At a nav beacon, you can use the KWS while you're doing the normal scan, but only shoot the guy if he's wanted. Basically, there's not really any reason to look at what the KWS tells you.
If you're collecting bounties, you'll get loads more at a high resource extraction site than at a nav beacon. There's a good one in the starter area in Dromi. Outside the starter system, LTT 15574 is always extremely busy and Haxel Port has loads of good outfitting plus a manufactured material trader, so you can collect materials as well as bounties.
As you are already looking in Nav Beacons , might i direct your attention to "compromised nav beacons"
More wanted criminals appear in those compared to the standard beacons.
You can locate a CNB (Compromised Nav Beacon) near you using this site. http://elitedangerous.hozbase.co.uk/
Just put a check next to "bounty hunting system" then type in the system your located at in the box below and select find.
Look for systems with a green check under the CNB category