If you knew enough to report a "mock" 1099-R when filing your 2015 return, the 1099-R you now have only confirms what you already reported.
Does the 1099-R you now have match the input that you used when preparing your 2015 return?
You have nothing to amend if you already accounted for this excess contribution in 2015. The excess contribution would have flowed to line 7 of your 2015 1040.
