The physical parameter well adapted to assess the degree of overmodedness of a reverberation chamber (RC) is the number $M_M$ of modes overlapping in a mode bandwidth. The lowest usable frequency of an RC often corresponds to a low modal overlap of one or two modes. Notwithstanding, in spite of this poor number of modes the RC still works. We show, using Monte Carlo simulation, that the number of modes must, in fact, not be restrained to $M_M$ and that the number of modes contributing to the field statistics can be, even at low modal overlap, somewhat larger than expected.