  We consider a phase transition from antiferromagnetic to phase separated
ground state in a spin-1 Bose-Einstein condensate of ultracold atoms. We
demonstrate the occurrence of two scaling laws, for the number of spin
fluctuations just after the phase transition, and for the number of spin
domains in the final, stable configuration. Only the first scaling can be
explained by the standard Kibble-\.Zurek mechanism. We explain the occurrence
of two scaling laws by a model including post-selection of spin domains due to
the conservation of condensate magnetization.
