My 48 acres of mineral rights I inherited

I did a lot of a lot of research and it’s 858 acres not 48.5 acres! I know I own a share not all acres but here’s the thing my grandmother only got 2 leases on tax inquiries and the 3rd lease there’s nothing on it but others heirs are so they me back pay for 12 years and not top of that back pay for 5 others leases they did not include my grandmother on in 2013 and 2014 that’s a whole lot of back pay!!!