A practical example: gross income of 1000 (=taxable amount)
assuming it's "des revenus d’activité" the total CSG deducted would be 9,2%,
of which 6,8% is "Taux de la CSG déductible"https://impot-sur-le-revenu.ooreka.fr/astuce/voir/507553/csg...so the starting gross revenu of 1000 would be taxed @9.2% for the CSG leaving 908 available,
but for the purpose of further taxes (mainly Income tax), the taxable amount would no longer be 1000, but will be reduced by 6,8% [which is "le Taux de la CSG déductible", so for further calculation of other taxes (the Income Tax and other) the "taxable income" would be reduced to:
1000 - 6.8% = 932 IOW these 6.8% would become in effect "non imposables à l'impôt sur le revenu"
In short: the ST (and my proposed translation) do make sense (at least in the convoluted taxman's logic).
So you would pay CSG on a taxable amount of 1000 and the taxable amount for Income Tax would be 932. (reduced by 6,8% "le Taux de la CSG déductible")