Hi Mark.
Based on what you want to achieve, I created a sample using my account I have 2 segments cktest and test. What I recommend is to send a broadcast to segment "test". Then the next day I can send an email to segment cktest but this time the filter should be like this:

This will send the broadcast to subscribers under the segment cktest. And I used another filter group that matching "none" (test segment), it will exclude the subscribers that are under the segment test even they are also under the segment CKTEST.