Hey there @Lancaster81786 -- great question! The short answer: your first date did not update because it had already been booked. The second date updated because it was not booked, yet. Let me explain further! 

When you set up a Group Event Type and choose the “Invitee Limit” per time slot, that applies to all future bookings. If you go into the event type settings and change that number, it will not apply retroactively to time slots that at least one invitee has already booked -- it will only apply to any future bookings that are brand new. 

In order to update the invitee limit for a time slot that is already booked (whether only one invitee has booked or all the invitee slots are taken!), you’ll have to: 

Head to your “scheduled events” tab > click “details” next to the desired time slot > click “edit invitee limit” > change that limit!

Next, you’ll edit the text field under “edit the invitee limit for this event” > click “apply”! 

You will have to do this for each time slot that already has at least one invitee booked, separately, in order to apply changes to more than one time slot. 

I wrote a comprehensive article going over how to do this: 

Good luck!