Hi TexasPeach,
As you go through the various taxation aspects that are personally applicable to you, I think you'd understand more of your specific scenario. A lot of others will be in a very similar position and it's why Tax returns are complex but also cover pretty much everyone.
That said, I used to work for Intuit who make TurboTax. I was involved in the QA and Testing side of things and no software - from any company for any use is perfect. It 'might' be a known issue or a program bug. I'm suggesting to you to look at the Intuit / Turbo Tax website and even log a support query. That way it'll be looked at with someone in the team familiar with Tax law and guidelines etc and they can confirm if it's an issue with the software or, a detail input error causing an incorrect result with what you see on screen. It might well turn out it's only an error with what you've entered so far as well, point is get it logged!
It's been a long time since I worked at UK Intuit and also covered the UK equivalent at the time - TaxCalc, so I'm sorry I can't point to a direct resolution for you ! Plus, I only had a limited few months and access to the US Turbotax product and knowledge of the USA tax setup/laws etc!
Cheers, DtM! West London & Slough UK!