N00b alert : error when flashing using esptool.py

I have the ESP8266 Breakout (HUZZAH) board from Adafruit. Been reading on how to get Espruino flashed onto the board. I'm on OSX so just running through the *nix instructions and got the latest esptool.py repo cloned and installed, according to the guide at;

http://www.espruino.com/ESP8266_Flashing

So the command I'm running is follows;

/Volumes/Data/Development/github/esptool/esptool.py --port /dev/tty.usbserial-AH03ILNP --baud 115200 write_flash --flash_freq 80m --flash_mode qio --flash_size 32Mbits 0x0000 "boot_v1.6.bin" 0x1000 espruino_esp8266_user1.bin 0x3FC000 esp_init_data_default.bin 0x3FE000 blank.bin

...but the error I'm getting is;

WARNING: Flash size arguments in megabits like '32m' are deprecated.
Please use the equivalent size '4MB'.

Sorry guys, I'm a bit lost, can anyone please shed some light? Also is there a better way to do this than the guide shows on espurino.com, from reading around quite a few forums I'm finding it hard to see the forest through all the trees (so many different ways to do this) ?

Most thankful to any help :-)