The “inorganic substances” may be adjustable as well.
The article does not specify if the percentages are based on weight or volume.
I suspect composition by weight may be more readily and reliably measured.
But, to me / for me, volume is the more pressing concern.
Hopefully, the “indigestible food matter” also makes up a significant amount of the volume.
to further cloud issues, Wikipedia offers:
The American Academy of Nutrition and Dietetics’ removed the low-residue diet from its Nutrition Care Manual because there is no scientifically accepted quantitative definition of residue and there is no method to determine the residue produced by a food.[13][20][21]
When it ain’t clear cut, go with your gut.
Haven’t done a colonoscopy prep yet, have you?
My understanding is that your digestive system tends to push at the same rate, regardless of volume. It’s not like a bladder that fills up, but just a long tube that pushes its contents along. It doesn’t get pushed solely by incoming matter. Furthermore, there’s the system of adding water that can help equalize the rates.
In my personal experience, the body tends to fall into a rhythm of a certain number of bowel movements per day, with the volume of the movement varying with input. The exceptions are only when some other condition causes diarrhea or constipation.
Cracked (not a medical Journal, but links to them) has pointed out several times (e.g 7 Basic Things You Won't Believe You're All Doing Wrong | Cracked.com) that the usual western Position of sitting on the toilet bowl knees bent at 90 degree angle is very unhealthy for the pooping process. They recommend a small stool to elevate your feet to a narrow angle, which means less stress to push the poop out (reducing strain in General - including the infamous-from-X-files “died of stroke while pooping”, but also lessens Chance of hemmorrhoids).
Obviously, you should check with your doctor on whether for your surgery, that type of sitting would help or hinder healing, but it might make less strain if you have to poop.
I could swear I saw something in Mad magazine 40 years ago, showing a cartoon drawing of a squat toilet with print copy below it saying something vague like “Some doctors believe that squat toilets are better for health.” They did not elaborate. I remember it because that was the first time I had ever heard of such a thing. I’m almost positive it was Mad magazine.
I think it may have been a drawing of a platform which you could put around your existing toilet to make it into a squat toilet.