In reference to your question, please see the detailed answer to another (highly similar) question on Royalty (rental) income that is posted here:
https://ttlc.intuit.com/questions/3621165
It has to do with income reported on a Form 1099-MISC as well. That advise, and those mechanical steps, should work the same for you too.
That said, with respect to the other part of your question, it would be a reasonable answer to say (and to input in TurboTax if asked) that your fractional ownership is actually 100% (of that fractional piece), as long as the income represented on your 1099-MISC is entirely yours, and you don't have to sub-divide it or share it among other landowners or inheritors. In other words, if you own 100% of the amounts shown on your 1099-MISC, then you can say you own 100% (for purposes of working with the tax software).
Thank you for asking this question.
