Note that the depletion allowance is 15% of gross, i.e. 15% of your royalty income before subtraction of severance taxes, before subtraction of deductions such as transportation, and also before any state or federal income taxes are subtracted.
Most years I have one or two Forms 1099 that don’t show the gross, so I go back to the check stubs to get the information for my calculation of gross. (I include a detailed workpaper as an Exhibit to Schedule E, showing how all the numbers on the 1099’s tie to my numbers.)