Keep column alignment with preformatted block text

Hello,

I'm playing with preformatted text, trying to keep my text same like
it was entered (same alignment).

I don't know why my text is not correctly aligned while using >>pre<< block ;
and why, the only working case I have found, is by using
[@
code
@]

test page is there :
https://www.pmwiki.org/wiki/Test/AlignColumn

Any advice ? Something I'm doing wrong ?
Thank you,
Gilles.