There are two categories of visibility within a note. A user can have full or partial access.
Having full access to a note means an attendee will be able to see all past notes that have been shared in the meeting stream and they will also be able to see any future notes that are added.
To give an attendee full access to past and future notes; this can be done by choosing the "all events" option in the original Google or Office Calendar invite*
Having partial access means an attendee will have limited access and visibility to a meeting stream.
If the option "This event" is chosen, the attendee with only be able to see the one specific note shared during this meeting event.
When the option " This and following events" is chosen, the attendee will be able to see the note from the current meeting event and all future events to follow.
How to see if an attendee has full or partial access
If an attendee was given partial access you can check who has visibility of a specific note by seeing what user icons appear on the top right of a note.
After clicking on the share button at the top right of the stream, If you scroll down to the bottom of the list, you should see the section that lists the attendees with limited access.
*It's good to remember that when a stream is shared via the "Share" button in the upper right hand corner of the stream, users will be granted full access to all of the notes in the stream regardless if they are guests or members.