There is an answer which helped me from another thread.
Answer: The narative definition of Form 1116 line 3ea is provided by Turbo Tax as shown by rogge1722. I carefully followed the definition adding each reference amount and had never been able to arrive at the same number Turbo Tax determined. The TT number was always much higher than my calculation.
I finally realized that I was interpreting the Schedule D instruction literally. I had a significant number of trades and the numbers appearing on Schedule D were net gain/loss figures. To get the correct value you have to go through each trade and add only the gains ignoring the losses. In my case that added a significant value to 3ea and I finally had a number that quite closely agreed with TT.
This drove me crazy for quite some time and I hope this explanation helps others.
With that persons advice I found the issue.
Thread: "How does Turbotax automatically calculate Gross Income from all sources on the Form 1116 3e? There is error in automatic calculation. My Mac does not open data source."
Link: https://ttlc.intuit.com/community/taxes/discussion/how-does-turbotax-automatically-calcu[product key...
