Dirk mimicked ("the sincerest form of flattery"):
> One cannot understand SR or even Galilean relativity if
> one doesn't even understand the concept of coordinates:
>   | "Let the unprimed frame's origin clock read zero when
>   | event E1 occurs at t = 0.6 and at x = 1."
>  https://home.deds.nl/~dvdm/dirk/Physics/Fumbles/MathProof.html

A mere glance at the site shows that Dirk is simply wrong.

It is easy to see that a the following single picture can
show the entire experiment:
(Note: a clock reading zero is shown as [0].)

Primed Frame            x=1
[0]--------------------[-.6]--->
E2                         E1
[0]--------------------[+.6]<---
Unprimed Frame          x=1

Note that - just as was said - the unprimed frame's origin
clock reads zero as event E1 occurs at t = 0.6 and at x = 1.

All readings and distances are given per the relativistic
transformation equations.

Contrary to Dirk, there is no clock which reads two different
times at once.

--kk--

 See also

https://home.deds.nl/~dvdm/dirk/Physics/Fumbles/MathProof.html

https://home.deds.nl/~dvdm/dirk/Physics/Fumbles/Competent.html