Sugar Camp Energy mineral lease in Franklin county in Akin area

We have been notified of mineral rights our father owned and been passed to the children. This company has offered $100.00 signing bonus. Also, a 4.5% royalty when coal is mined…This 4.5% will be paid MINUS…all chgs assessed by purchaser, taxes due to production, sales and a whole list of expenses, and Transportation costs…this seems strange to me. We are not in coal business…why should we pay for all this out of 4.5%??? It may be normal…just needing advice from someone who knows… Also…even though it is only… .59 of an acre, I still do not want to be taken advantage of. 2 siblings already jumped at signing for 100.00 Just don’t like to jump this fast without information… Thank you all for your time and consideration in this matter. I appreciate your help!!!