It only makes a different specific to the crank, too long or short and it will screw up the chainline. For the compact FSA it should be 108mm width spindle, as most double cranks are right around this range. The 113 should be for mountain bikes, 118 for triple cranks. If you still have any doubts, check the info for it in almost any online shop, it should list the bb spindle length (now you just have to know if you need 68mm threading or 73mm (68 being by far the most common in my experience)).