Growing comfrey:
Each root piece of an inch or so will usually make a new plant. Most of what I have sent you are full root crowns which could be chopped into more pieces if you want more plants (but slower establishing). If you want 10 fast plants keep each piece In tact. If you want double or triple that you could probably divide these further (if your site is pretty easy for them/not too much competition like grass.)
Insert into soil 1-3” and as long as it’s not in super arid soils or very dense sod you will have a new comfrey plant within a few weeks or so.
PLANT THEM ONLY WHERE YOU WANT THEM FOREVER! They are an incredibly valuable plant but are very hard to remove. Don’t put near a vegetable garden. These are sterile and will only spread by ground disturbance. You now have comfrey to multiply as much as you like.