Topping will depend how many branches you want you overall. If you have 3 nodes thats 3 sets of branches from the soil giving 6 branches that will come up, same at the 2nd node have 4 branches and the 2 branches from the 1st node.. Also tho to add to this you can then also top the branches... So at 3rd node will give 6 branches ye.. Top those branches and you now have 12 branches and so on.. 2nd node gives you 4 branches, top those and you have 8... 1st node gives 2 branches top those you have 2. This can be done over and over again if you like.. So 1st node starting with 2 branches giving you the main manifold to keep topping and end up with countless branches. This works for every node and every branch... Hope this help you to understand the principle.. Good luck growmie