The modulated magnetic ordering and the atomic position modulation are studied in the case of the multiferroic CaCuxMn7-xO12by neutron and SR powder diffraction methods. Below the magnetic transition temperature of $T_{\text{N2}}=50$ K both orderings are described by using the magnetic superspace group R31$'$($00\gamma$)ts. For the magnetic ordering two different incommensurate modulation vectors are used: $(0,0,q^{1}_{m})$ and $(0,0,q^{2}_{m})$. For the atomic position modulation only one modulation vector is needed $(0,0,q_{p})$. The magnetic ordering is of helical screw-type showing beats in the magnetic moment spatial distribution. The values of $q^{1}_{m}$ and $q^{2}_{m}$ change with temperature below $T_{\text{N2}}=50$ K but the average value fulfil the relation $(1/2)(q^{1}_{m} + q^{2}_{m}) = (1/2)q_{p} = \text{const.}$ This relation underlines the importance of the magnetoelastic coupling in CaCuxMn7-xO12compounds below $T_{\text{N2}}=50$ K.