It's not a 1/1 change. Normally, you can go up or down 1 tooth up front with no change in chain links. When changing length, it must always be an even number, ie; you can't just drop one link.
FWIW - The B12 comes with a 110 link chain and 15/45 gearing. So if you go with a 112 links and it's too long, you could just cut a pair out and make it a 110.