This is just a simple mystery for Split airport travelers or visitors to shorten their time while waiting for flight home.
Key to enigma can be found on GC8401R Lost place - Phone box #44.
To get final coordinates of this cache you need to add "even" number found on GC8401R to both starting coordinates of this geocache coordinates, N and S, simple as that...
...and have fun geocaching in Croatia!
Do not look for this cache in a stonewalls, do not ruin them, they are hard to be rebuilded after geocachers.