Split ventrals means there are one or more points at the end of the ventrals, the fins resting under the body. Ideally you want only one point and for the ventrals to go straight down and be even with each other. I can throw up an extream version of split ventrals for you from a breeder I know in Canada and then normal ventrals to help you spot the difference.
Case of serious splitting which though he is a great male the breeder will never breed him.
First one I linked since the photo is too big.