Don't be. For the most part, it is all meaningless. In the context of what it is supposed to be all about -- the only thing that is meaningful would be something like:
You know that you have a 'Fruit Loops' box stored away in your attic. You know that the same [ original ] box has been there for 50 years. You are absolutely convinced beyond-a-shadow-of-a-doubt that the spelling on the box is 'Fruit Loops'. You retrieve it from your attic, only to discover that the box reads 'Froot Loops'.
If you retrieved the box from your attic, and the box read 'Fruit Loops' --- it would then be meaningless as far as the Mandela Effect is concerned.
If it used to be 'Fruit Loops' - and it is now 'Froot Loops' --- it only means that they have changed it at some time between then and now.
That being said --- I am quite convinced that there were only 4 people in the JFK limo.
However, the point of this post is -- do not let the "apparent" / "seeming" change-in-the-so-called-facts "rattle" you...
After doing a bit of research on it, I tend to agree with the folks that say it is a PSYOP. After all, the absolute-majority of all of the stuff you see on the internet concerning the Mandela Effect
can be very easily manipulated...
( including the Zapruder film
)