We fitted the data obtained from the susceptibility measurement performed on polycrystalline samples with two different sets of microscopic parameters. One set (a) contains only single ion anisotropy and the other (b) both single ion and exchange anisotropy. None of them can be favored on the basis of powder experiment. We demonstrated by means of quantum transfer matrix and exact diagonalization calculations that parameters with only one type and those comprising two types of anisotropy lead to qualitatively different behavior of magnetic susceptibility and torque calculated for a mono crystal. On the microscopic level me observe that the first anti-crossing gap between the ground and first exited states vanishes when two types of anisotropies (single ion and exchange) of different orientation (easy axis and easy plane) and similar magnitude are present in the system.