Question on Daikin DIII net protocol

[kevinzh]

Hi there
I'm using Daikin Modbus module (DTA116A621) with LM3 for home AC control. 
The profile provided by the engineer is as below: 

{
  "manufacturer": "Embedded Systems",
  "description": "DAIKN-DTA116A621",
  "mapping": [ 
 
    { "name": "on_off_status_00",  "bus_datatype": "bool",    "type": "inputregister",  "address": 2000,  "value_bitmask":0x0001},
    { "name": "set_temp_status_00", "bus_datatype": "float16",  "type": "inputregister",  "address": 2002,  "value_multiplier": 0.1,  "units": "C"  },
    { "name": "act_temp_status_00", "bus_datatype": "float16",  "type": "inputregister",  "address": 2004,  "value_multiplier": 0.1,  "units": "C"  },
    { "name": "on_off_00",          "bus_datatype": "bool",    "type": "register", "writable": 1, "write_only": true,  "value_base": -4352,  "value_multiplier": 1,    "address": 2000},
    { "name": "set_fan_00",        "bus_datatype": "uint8",    "type": "register", "writable": 1, "write_only": true, "value_base": 0.45684814453125, "value_multiplier": 0.0001220703125, "address": 2000},
    { "name": "set_mode_00",        "bus_datatype": "uint8",    "type": "register", "writable": 1, "write_only": true, "address": 2001 },
    { "name": "set_temp_00",        "bus_datatype": "float16",  "type": "register", "writable": 1, "write_only": true, "value_multiplier": 0.1, "address": 2002, "units": "C"},
......

in reality the fan-speed control does not work properly - it does not change in consistence with the setup on user interface (ABB wall-mount sensor control), and in certain speed settings (esp at low speed) the fan makes troubling noises

just wondering how the value-base and value-multiplier are calculated and chosen in this case, and how i can make changes to make the setup work right.
i also attached Daikin's protocol below

thanks in advance

Wang