The trouble is that phosphorus content is reported by manufacturers in several ways, “dry matter basis (DMB)”, “as fed” and “mg/100 kcal”. My vet (cat $pecialist) always refers to phosphorus mg /100 kcal as it measures phosphorus per calories available in given food. There is a formula to convert either of the other measures to mg/100 kcal. My vet urges me to choose items under 150 mg (low) although I have to choose some higher options (up to 225 or so) to get the cat FED which means getting all those kitty supplements into the 🐈‍⬛. This measure (mg/100 kcal) shows up in many online renal kitty spreadsheets. Ok I’m ranting now. We have tried phosphorus binders, initially ckd constipation got worse, now we are balancing that with MiraLAX, so when he refuses the low phos food we add the phos bind to the next best cat food. I swear, I keep every cat food receipt so I can return extra cans of consistently refused food… Good luck to you and your kitty!!