If you are on a "five-year distribution"schedule, then distributions from the inherited IRA are considered "RMDs" and the entire amount of that distribution is an "RMD".
From RMD rules for inherited
IRAs :
RMD calculation methods
The 2 methods to calculate your RMD—that is, how much you must withdraw—are the life-expectancy and 5-year methods. Qualified trust beneficiaries follow unique distribution rules, which are explained below.
Life-expectancy method
The life-expectancy method requires that you withdraw certain amounts from the IRA each year according to IRS calculations. You can withdraw more than the RMD if you wish.
5-year method
The 5-year method requires that you receive the entire balance of the account by the end of the fifth year after the year of your spouse's death.
You may make withdrawals at any time, as long as you redeem the entire account balance by the end of that fifth year. The 5-year method doesn't apply if the account owner dies on or after his or her required beginning date.
