Per the Settlement Statblock in the Gamemastery Guide, the various modifiers affect skill checks in the settlement (Thornkeep). I've compiled them here for a quick reference:
+2 to bluff city officials/guards.
+2 to stealth (outdoors only)
+1 to intimidate when forcing a friendly attitude
+1 to diplomacy v. guards/officials, and to gather information
+1 to knowledge checks using city resources (libraries, etc)
+1 to perform, craft, and profession checks to earn income.
-2 to disguise, and diplomacy v. non-govt NPCs.
Not sure how often people pay attention to these, but they're here for your convenience!