Shimano sora 9 Speed rear derailleur capacity Rd-3500 SS I'm having a go at replacing a drive train for the first time.

It's a 9 speed, and I've ordered a compact chainset (50/34), and 11-28 cassette (all Shimano). To go with them, Ive ordered a RD-3500 SS derailleur.

On the Shimano website, the specs said capacity 37T, which by my reckoning, should be enough (50-34)+(28-11)= 33.

However, now that its arrived, the logo on the box says "Max 32T"- i.e, 1 less.

Will this be a problem (do i need to change for the medium cage), or is there usually enough tolerance in the spec? 

Does this maxiumum capacity only come into effect if 'crossing the chain'? (of course, one should avoid doing that anyway)

many thanks
Max 32T here refers to the largest rear sprocket, not the total capacity. So with an 11-28 you'll have no problem.