It basically has to be 2 days on either side, because the training has a 12 (I think) hour buffer with it on either side. Lets say you have a block of Rdays that ends with an Rday on Friday- you bid for training that goes Wednesday and Thursday so you think you're winning. But the training buffer removes the last Rday so you're not truly splitting the block. I know because it's happened to me many times.