Some clarity about making Delia’s Seville Orange Marmalade

I have been using your Complete Cookery Course since the late eighties, and you have become my constant and reliable kitchen guide.
However, I do have a question regarding the Seville Orange Marmalade recipe. I know that the pips and pith need to be added to a muslin bag to extract pectin, but what about the pulp that remains after squeezing out the juice? I remove that, and also remove as much of the white pith on the inside of the peel, but what do I do with it? Instinct suggests adding it with the juice and the rest, but your recipe is silent on that point. Is it also to be added to the muslin bag, or does it go in with the juice, water and sugar and finely sliced peel?
With regards,and thanks,
Tony Stockton