Mineral Taxes in Block 71

We have owned almost a section of land since 1927; now in a family trust. We are part of two pooled units where drilling began early in 2020, though not on our land. We paid the real property taxes back in November. Not much different than normal. We have an agricultural exemption. The mineral tax assessment is roughly 10 times the real property valuation but there is a “less production assessed” line which removed 98% of the valuation, so the result is a $35 tax bill. The valuation is about 14% of the royalties the trust received in 2020. Not complaining, but I was expecting a much bigger tax bill, so I am waiting for the other shoe to drop. I am a bit confused and also suspicious that they made a mistake I will have to pay for later. Any assistance appreciated.