The legitime of each of the acknowledged natural children and each of the natural children by legal fiction shall consist of one-half of the legitime of each of the legitimate children or descendants.
The legitime of an illegitimate child who is neither an acknowledged natural, nor a natural child by legal fiction, shall be equal in every case to four-fifths of the legitime of an acknowledged natural child.
The legitime of the illegitimate children shall be taken from the portion of the estate at the free disposal of the testator, provided that in no case shall the total legitime of such illegitimate children exceed that free portion, and that the legitime of the surviving spouse must first be fully satisfied. (840a)