There are two forks of CDC. That's why there are different starting heights.
228898+ is the old chain which is stuck (PoS only, no PoW). Only older clients v1.0 (/Satoshi:0.7.2/) will be on this chain, but newer clients can use it to partially sync.
282957+ is the newer chain, which all clients can use: v1.0 (original), v1.1, v1.2.
CDC is hard to mine because PoS fights with PoW; a single PoS block can orphan the end of the chain that contains PoW blocks. Mostly this is just one or two blocks, but sometimes it can be 10+ blocks that are orphaned and replaced with the PoS block. CDC is not the only coin which is PoS heavy.
