The 1234 is the main file folder for that individual save game. Click on it, there should be a drop-down submenu with an entry that reads "1234 [Main]" that when selected will activate the Play Game button. At any time during gameplay, the F6 key will add a new entry in the submenu so you can save a snapshot of that place in the game, and it will be neatly filed under that 1234 folder with "1234 _SUB_#". It's just a more organized menu layout.
