Yes, that's the correct error message you get when you enter more than you should.
There's an option to enter a lump-sum payment. The reason it's entered separately is because the taxable amount for each year needs to be figured. Make sure you have that year's adjusted gross income to correctly compute.
I'm not exactly sure how to get there in Mac, but you'll find it as a separate category in your Retirement & Social Security section under Income.
