Hi @Group Administrator (Rob - not used for email) ,
maybe this link is helpful to find the answer:
https://learn.microsoft.com/en-us/microsoft-365/bookings/bookings-faq?view=o365-worldwide#what-if-my-organization-has-mixed-licenses-with-f1-f3--e1--and-e3-e5-
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(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)
Regards
Andreas Baumgarten