This is a process created by some japanese nuerseryman in japan. His article was published on how he grows awesome JBP shohins in 10 years(i question his results in 10 years, but thats beside the point). Anyways, to properly answer the question, you treat the seedling like a cutting to encourage the beginnings of an awesome nebari. From my previous experience, I ended up with 3-7 roots emerging from the point on the stem where I originally cut. This is a far superior start to producing an excellent nebari than constant root pruning. Two means to an end, but one has proven to be more effective.