All companies define NPRI’s differently. Your questions are quite confusing. Guessing these are older royalty deeds, the 1/8th simply refers to all royalty for the mineral owner. But, you have to account for the % granted and then how many mineral acres the mineral owner owned at the time for each tract of land. A NPRI is carved out of the mineral owners royalty interest. Im not sure what you mean by subsituted, but your % interests stay the same if the NPRI was done in 1 conveyance covering all of the properties mentioned, if they come in multiple royalty deeds, well thats whole other can of worms. But, the only thing that changes would be the new oil and gas royalty that leases were taken under after you got the NPRI. Whats the approximate amount of the owner fees that you are being charged per month? This seems to be what you are trying to fight? If its not much, Id drop it and move on as this will cost you quite a bit to figure out as NPRI’s are the most complex title for mineral owners especially when company B has been paying you for quite awhile on the majority of your interests