You and I share the error, [MENTION=6799753]lowkey13[/MENTION]. I vetted Brinn's sheet very carefully, and thought (mistakenly) the +3 attack bonus was correct because Brinn's Strength 12 and +2 proficiency bonus combined for a total attack modifier of +3. What I missed, and I apologize for my error, was that a monk may apply either his Strength or his Dexterity bonus to attack and damage rolls for unarmed strike. With a Dexterity of 16, you are quite correct, Brinn's attack now goes at a +5.
I'm glad you spotted the mistake. But sorry it took us so long to get there. Boo.