Questions about mineral rights ownership vs. royalty ownership

Situation: Individual A owned 160 acres of land. Individual A sold this quarter of land to Individual B, but reserved 1% mineral interest of oil and gas discovered in future. Individual B then sold 160 acres of land to Individual C, but reserved 6.25% royalty of all oil/gas produced.

When Individual C passed away, the final decree was written incorrectly and 100% mineral interest were passed on to heirs, reserving 7.25% royalty (the incorrectly combined the 1% mineral interest and the 6.25% royalty interest). Corrected, it should have read 99% mineral interest passed on, reserving 6.25% royalty.

The error will be corrected by a stipulation and cross conveyance. However, my question is: If the heirs of Individual A have been receiving 1% of the royalty, instead of 1% of the mineral interest, have they been receiving more $ or less $ than they should have received?

If the lease were 12.5%, it would seem to me that receiving 1% royalty of 12.5% would be financially greater than receiving 1/160 of the 13.75 left over after the 6.25% share of Individual B is taken out.

Is my understanding/math correct on this? If not, please explain. There is no feeling attached as the error made by legal counsel years ago was not intentional and likely understandable, but as a newcomer, I am simply curious as to how this all works. Thanks so much in advance to whomever might clarify this for me!