This can happen if you specify that the software should use required minimum distributions (which is the default mode of calculating distributions), but you start distributions before age 70.
The IRS requires that distributions start at age 70 1/2, but it does not provide any definitive method for calculating “required minimum” distributions before that age.
We use the IRA Mortality table I, from IRA Publication 590B, for years before age 70 1/2.
At age 70 1/2, we switch to the prescribed retirement table, Table III.
If you want to show different distributions, you may override the software’s calculation of the distributions.
To do that, click “more info” on the IRA asset and scroll to the line labeled “Click here to View/Edit Annual Distributions for [Party Name].”
Then enter the annual (not monthly) amount for each distribution.