Yes, you're quite right - but it's not very clear from their web site that this is the case. You have to look at each set of plants individually to see whether they are available in vob format (I didn't look at every CD but the ones I did look at all were). That's quite an important selling point, they should make it a little clearer.

It seems that each CD has 20 plants with three size variations of each, but for more variation you would need the Xfrog software.

Steve