Two sales - primary residence and duplex (formerly primary)

[Matthew R.]

I’m new to this side of things, as these would be my first sales of real estate.  

I have a duplex in which we lived for over two years within the past five years (Dec 2016-Apr 2019) and also a primary residence in which we have lived for over two of the past five years (Apr 2019-present).

If I’m reading the capital gains tax rules correctly, only my current primary residence can be exempt.  Am I understanding this correctly?  I would love to be wrong...but want to be sure either way.