Intrest paid on Oklahoma Royalties

Greetings, As I am new here I hope this finds a knowledgeable person…

I have had money held and not paid which was their fault. They did pay interest at the 12% rate but didn’t pay on the first six months of production. If I am interpreting the statute correctly they should have to pay after the six months but interest would be due because they didn’t pay in a timely manner. Can someone please clarify the wording on the statute for me. Thank you in advance.