im not sure if you got the answer you were looking for, but:
ex, B18C5
B=engine family (series)
18=displacement (1.8L)
C=version displacement (which version of borexstroke it has. ex: B18B has a different bore and stroke, but makes the same displacement "1.8L", so C is used to identify this engine from the B18B)
5=version of engine using same bore and stroke (its the 5th version of the B18C they made which had enough significant difference from the last one to give it a new name. such as different pistons, ECU, intake manifold, head casting, cams, etc.)
of course there are exceptions, but this is generally how it works. the only one i can think of right now that wouldnt work is the B18A and B18B, since they both have the same bore & stroke.
other then that, it all makes sense, since honda always comes out with the A-version of displacement first (F22A, H22A, B16A, B18A, K20A, K24A, etc.) and so on.