Kyle, from the small amount of info in your post, it appears that you only own 3.125% of the minerals in the 74+ acres in question. The 21% royalty would be what the company is willing to give you for royalty on any production that takes place associated with this lease and any unit this lease may be part of. You mention vertical well - has one been drilled already? Or are they talking future wells? And what about horizontal wells? These are common in parts of Fayette County - but if the 74+ acres is part of a horizontal well unit, it will only be a fraction of a several hundred acre unit. You also have not mentioned any bonus numbers or lease term/time frame. There is no way to know how good any well can be but one can get an idea of potential based on historical and trend activity. A lot depends on where your acreage is located. What are the full details of what you are being offered? Do you know which company wants to lease your minerals?