I am trying to use localtax1_assuj localtax1_value

While I understood that enabling the localtax1_assuj in the rows of table llx_societe allows for the localtax to be calculated and shown, I cannot understand what is the use of localtax1_value in the same table ( and so on for localtax2 ).

Do you have a screenshot? did you use Dolibarr as already implemented or you are trying to understand the software?