A 34/35 sleeve length shirt actually has a sleeve that is 34.5 inches. in length. The 34/35 is an indication that someone who wears a 34 or a 35 can wear the shirt. The combo sleeve lengths are typically used by mass manufacturers who are looking to cut down on different sizes that they would otherwise need to carry.
Dress shirts rely on two measurements, neck size, and sleeve length. The neck size appears first, and increases by half inches range from 13" to 19". The second number is the sleeve length. ... A good dress shirt manufacturer will also provide a chest measurement range within a given size.