Inherited IRA RMD amount requirenment

I've taken my distribution and entered my 1099-R distribution data in TurboTax Desktop. Now it requires I fill in an amount for the RMD due by end of calendar year. The best I can research states that as an ineligible, child beneficiary, I must follow a 10-year distribution rule to deplete the inherited, traditional IRA from my mother.

Do I enter '0' for the required RMD in TurboTax because there is no IRS table to calculate a RMD? Or do I prorate the balance over the years remaining and insert that value?

My question only is what I enter in TurboTax for the minimum required RMD. I've already distributed a prorated amount of the total balance.

Reviewing IRS 590b it appears that I can distribute a prorated amount of the IRA each of 10 years or take a lump sum at the 10th anniversary. So is this question about declaring a minimum RMD a TurboTax artifact or is their some IRS requirement that is used to determine a minimum?