Phillip didn't die at count number 7.  In actuality, they counted to ten, George and Phillip turned around, stared at each other, then George shot. 

"At the duel, Philip Hamilton heeded his father's advice and did not raise his pistol at the command to fire. Eacker followed suit, and for a minute, the two young men stared dumbly at each other. Finally, Eacker lifted his pistol, and Philip did likewise. Eacker then shot Philip above the right hip, the bullet slashing through his body and lodging in his left arm. In what might have been a spasmodic, involuntary discharge, Philip fired his pistol before he slumped to the ground." Chernow.

A/N:

Found in Ron Chernow's Alexander Hamilton.  Idk what page.  I actually copied it off of here:

http://genius.com/Lin-manuel-miranda-blow-us-all-away-lyrics

They said it was in the book.  I trust them.