If the tag’s output is not a numeric type, it will be considered as being 0 (zero) and the filter will simply return the negative value of the argument that was passed to it:[(#TEXTE|moins{18})] will return «-18».
It is possible to assign a negative number as the argument to the filter: [(#TOTAL_BOUCLE|moins{-5.2})], but this would undoubtedly be more clear if we were instead to use the |plus (add) filter.
Warning: if xx is a floating point number, it must be written with a period as per the English method as opposed to being written with a comma as some European languages do: [(#TOTAL_BOUCLE|moins{5.2})].