Burr: They delighted and distracted him , Martha Washington named her feral tomcat after him
Hamilton: That's true
I think when Hamilton says 'that's true', that's when he broke the fourth wall.
I'm not exactly sure, cause I didn't notice any 4th wall breaking myself in that song, but I searched it up and looked through some links and they said that it was that part.
I hope this helps! Good luck!