What can I do if there is discrepancy in land share?

My late father had bought a piece of land. After his death, my mother and I completed the mutation process, as we are the sole living heirs. This year, when I deposited the khajna (land revenue), I noticed that my mother’s share is shown as 60 and mine as 20. My question is: where is the remaining 20? After carefully checking the mutation papers, the same discrepancy was found. I am very confused about what is happening.