Finally I get where the issue comes from :
My db is a MS SQL 2017 and actual / Budget are defined as Money. When I went through the Data Manager I saw that my numbers are preceded by " ' ". I don't know why ??? The workaround I put in place is to create calculated field that force actual to numerical value by multiplying it by 1 and then of course NumericalAbbreviation worked fine.
Any insight why in Qlik Sense my db money values are preceded by " ' " ?