Most plants don't branch out much naturally indoors. It's sort of an unusual situation to have side branches with their own separate nodes ready to top at the same time as the main stalk's first topping. You can do it, though. Topping stops the growth of a stalk so that in order to grow, the plant needs to do so through the two little shoots at each node. For best results, you should usually only top the tallest stalks. While those topped stalks focus their energy into growing the shoots at their nodes, the lower shoots begin to catch up with the rest of the canopy. By flowering, the grower aims for the tops of all stalks to be at the same level, receiving equal amounts of light and creating a canopy of buds.