Figured it out Lol. I love a good old mystery puzzle ;)
- Luffy’s number during the Dressrosa arc's tournament is 0556.
- Luffy was born on May 05, so that explains the “05″ part,
- 5-6 is actually go-mu in japanese, which makes sense coz Luffy is rubber (gomu),
- So that explains the “56″...