Free Royalty retained by the Stae of Texas

When we purchased our property from the State of Texas in 1948, the State retained a free 1/16th royalty according to the deed. My royalty interest is 1/8th. The state’s royalty interest comes out of my royalty interest, reducing my net interest to 1/16th. My question is why is it coming out of my portion 1/8th and not the remaining royalty interest? My deed and lease do not state that it should come out of my portion. Any help would be appreciated.

How is your lease worded? Do you have production which is decades old? You may need to provide more details as to location, etc. Meantime, consider reading this and/or opening the GLO’s map viewer.