Oh, I see, so you are working with Nicolet files. The segment splitting is specific to this format, hence my confusion. We are using an external function to read them in Brainstorm so we have limited support and understanding of this format. I believe the original repository for this function is the following if you want to ask the creators a question: https://github.com/ieeg-portal/Nicolet-Reader
One thing I can add by looking at their code is that the Nicolet files seem already segmented. Therefore, the arbitrary number of 7 segments in your case is most likely decided at the level of the acquisition system.
I hope this helps,
Martin