You dont count the first set of single fingered leaves. The first set of 3 fingered leaves counts as one node. The 2nd set of leaves above it (3-4 fingered) is the 2nd node, and so on. By the pics it looks as though you are starting your 3rd set of leaves or 3rd node. Normally people top at the 3rd or 4th node or between like days 14-21. If you want to top at the 3rd node, wait till the leaves for the 3rd node are actually grown out. Same goes if you wanna top at the forth node, wait for the leaves to grow out a little more so you can get to the main stem. There are several techniques to choose from. This is the technique I use.. (About the 4 min mark)