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 does not state that it should come out of my portion. Any help would be appreciated.

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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.