() are the beginning and ending of a group. Whatever was found inside that group is replicated in the ReplaceWith box by using \1.

Finding [0-9,] means the find will find any digit or comma. Including an @ after that means it also finds more than one character instances of that pattern. It is the same as including {1,} instead of the @

If you want to also include periods you just include that in the pattern
Find = \[([0-9.,]@)\]

__________________
Andrew Lockton
Chrysalis Design, Melbourne Australia