Main entity defines relation between tables in your query
If you selected Session as a main entity the relation to full SQL is 1:N so in the Full SQL column you will have number of SQL visible in this session.
Read more for example from my blog:
https://guardiumnotes.wordpress.com/2017/10/06/guardium-reports-platform-understanding-1/
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Zbigniew (Zibi) Szmigiero
IBM
Międzyrzecz
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