How to find Jelly's share safe combination?
The code you're looking for is behind the bottles.
The first key code combination in LGS games, and since their demise companies who follow on in their spirit, is 451 or a variant thereof (e.g. 45100). This is a reference to Fahrenheit 451.
This means you can guess the combination quickly without even looking!
This tradition started in System Shock 1 and is followed by System Shock 2, Deus Ex, BioShock and now Dishonored :)
Have you look this video on Youtube?