DFR0971

I have recently purchased some DFR0971 boards and following the sketch on this page, https://wiki.dfrobot.com/SKU_DFR0971_2_Channel_I2C_0_10V_DAC_Module by sending data 4095 to the board I should get 10V output, however I get 4.1V, it seems that the calculation for putput voltage is different to that staed and the data is actually the output in mV, i.e. to get 5V I need to send 5000, 6V 6000 etc. Has the firmware changed?