As I said, but actually you should treat it as "Sxxx-xxxxx", as you have such as SCUS, SLUS SCES, SLPS, etc....But good advice anyway, as chaining them is how you keep PEC inline with the game where you may need to change discs.
Following the code on the binder (especially the prefix) is important for that to happen. For the above example, "SLUS-94455" will not work with PEC for finding the same game disc, as this code does not match the header on the physical disc. For "Colony Wars". You'd enter
Code:
#Colony Wars#SLUS-00554#SLUS-00543
because disc one has the ID "SLUS-00543, and disc 2 has the ID "SLUS-00554. The order does not matter so long as you include all discs. For most (if not all) discs, the actual disc ID is printed on the label of each disc.