Segment comparison for Target test experiences

We recently launched a new test and I wanted to check if the customers can enter both A & B experiences. I know in theory the customer should always enter the initial experience, however, I've seen cases where the same customer saw both A and B experiences in our Tealeaf session.

Segment1(Hit container):

Activity Test = XYZ & Experience = A;  

Segment2(Hit container):

Activity Test = XYZ & Experience = B;

I build a segmentation comparison using these 2 segments and it shows ~400 unique visitors overlap. Does that mean the customers will enter both experiences? If so, what are the scenarios that can contribute to the overlap?