Twelve minutes is the default
A meeting reminder tells you that a call exists. It names a time, a link, and sometimes a title. By the time you need it, you already know those things. What you do not have, unless you went looking, is the person.
The brief is the other email. It arrives before the call, in your mail, and it carries the record of the people you are about to meet. The point is memory. You should be able to open it, read who is about to be on the line, and close it before you join.
Where the twelve minutes came from
Twelve minutes is long enough to read a record and short enough that the reading is still in your head when the call starts. It is also early enough that you are usually at the desk, not already talking. That is why it is the default.
It is a default, not a rule. People do not prepare on the same clock. Someone who lives in back-to-back calls wants the record when the previous call ends, which may be five minutes out. Someone who reads on the train wants it half an hour out. Someone who prepares the night before wants it then. Forcing one clock on all of them makes the mail easy to ignore.
You change the time. The mail is the same mail. It still does not need to restate the hour of the meeting or announce what the meeting is for. Your calendar already did that. The brief is the people.
What is in the mail
The record is the person you are about to meet, in full enough that you are not reconstructing them from a title. Work, education, places, languages, a birthday, skills, interests, and the profiles under the name belong on that record when we have them. A photo, a phone, and an email belong there too, as facts, not as a row of links you are expected to tap during the read.
If more than one person is on the invite, the mail has those people. It is not a digest of everyone you will meet this week, and it is not a note about who has accepted. Acceptance is a calendar state. The brief is the record.
The timing change does not thin the record. Moving it from twelve minutes to twenty, or to the evening before, does not turn it into a different product. You are choosing when you want to remember these people, not which facts you are willing to see.
What you should not have to do
The usual preparation is a search. You copy a name out of the invite, open a profile, open the company site, and hope the tab you meant is the one still focused when the call starts. That work is real, and it is also repeated. The next call with the same person asks you to do it again, because the reading lived in a tab you closed.
The brief is that reading, delivered. You do not assemble it. You also do not have to be in Chrome, and you do not have to have the calendar event open. The mail is enough. If you want the same record earlier, beside the event itself, that is the calendar. The mail is the one that comes to you.
Set the time to the minute you actually read. Leave it at twelve if that minute is twelve. The record does not care which you pick.