code: def read_sizes(self):
          
          command = const.CMD_GET_FREE_SIZES
          response_size = 1024
          cmd_response = self.__send_command(command,b'', response_size)
          if cmd_response.get('status'):
              if self.verbose: print(codecs.encode(self.__data,'hex'))
              size = len(self.__data)
              if len(self.__data) >= 80:
                  fields = unpack('20i', self.__data[:80])
                  self.users = fields[4]
                  self.fingers = fields[6]
                  self.records = fields[8]
                  self.dummy = fields[10] #???
                  self.cards = fields[12]
                  self.fingers_cap = fields[14]
                  self.users_cap = fields[15]
                  self.rec_cap = fields[16]
                  self.fingers_av = fields[17]
                  self.users_av = fields[18]
                  self.rec_av = fields[19]
                  self.__data = self.__data[80:]
              if len(self.__data) >= 12: #face info
                  fields = unpack('3i', self.__data[:12]) #dirty hack! we need more information
                  self.faces = fields[0]
                  self.faces_cap = fields[2]
              return True
          else:
              raise ZKErrorResponse("can't read sizes")
docs: read the memory ussage