transfer partial asset values from completed asset to AUC/other asset

It is obvious that you are not paying attention. You already received a good answer to your question. Had you bothered to look at the transaction (ABUMN) you would see the different tabs and especially the one labeled (PARTIAL TRANSFER). Since that is what you are trying to do, it would seem logical that you would look at that tab and see that you have options -- doing a partial transfer based on amount, quantity or percentage. You need to do some of the work yourself.