Beads Molar volume "Synthia"

Dear All,
I'm calculating solubility parameters ( CED method) for DPD simulations. I'm working with a PLGA copolymer. I have two types of beads : one bead with three lactic acid monomers and the other with three glycolic acid monomers.
I'll explain the case of the lactic acid bead (three monomers).
In fact, to obtain the molar volume in ( cm3/mol). I'm using the synthia module, chose homopolymer, load the repeat unit ( one lactic acid) and i define a mass of 270 g/mol corresponding to three lactic acid monomers ( for synthia, this should be considered as a homopolymer of three repeating units). I have obtained a molar volume of 61.41 cm3/mol.
To be sure, i loaded in synthia a fragment constitued by three lactic acid monomers (same composition of my beads), i define a mass of 270 g/mol but i obtained a molar volume of 143 cm3/mol.
Wich value i am supposed to use knowing that my dpd values ( rc and mass) will depend of this results.
Thanks a lot for your help.
Best regards