Thanks (yet again) Bob.
I'm very familiar with 2's compliment but that was why I was a bit thrown off course by the API using "unsigned int's" and what the implications of this would be.
Not easy to write a datasheet and staying simple. Providing to know the word "two's complement" makes the elaborate more valuable than using the term "signed int". And providing a signed result as an unsigned function return is ... well, ... nasty
I would suggest you to create a support case to point Cypress to this ambiguity.