Murray serves first
The one who serves first can serve 5 and other will serve four.
If Murray serve 4 and Djokovic serve 5
Then five service breaks and Murray winning 6:3 not possible.
Murray serve 5 and Djokovic serve 4
There are five service breaks and score is Murray 6 - Djokovic 3
On Murray serve, Murray wins 3 and lost 2
On Djokovic serve, Murray wins 3 and lost 1