Why 1233?
Because he fought Zolo in chapter 51 the first time.
Zoro uses 3 sword style
51x3=153
AI Overview Roronoa Zoro's "1080 Pound Phoenix" (or Senhachijū Pondo Hō) is a powerful Three-Sword Style flying slash technique from the anime and manga One Piece.
1080
51x3=153
1080+153=1,233
Zoro is going to face Mihawk in chapter 1233
Because he fought Zolo in chapter 51 the first time.
Zoro uses 3 sword style
51x3=153
AI Overview Roronoa Zoro's "1080 Pound Phoenix" (or Senhachijū Pondo Hō) is a powerful Three-Sword Style flying slash technique from the anime and manga One Piece.
1080
51x3=153
1080+153=1,233
Zoro is going to face Mihawk in chapter 1233