I'm reading this datasheet: http://www.jaycar.co.nz/products_uploaded/ZD0012%20-%20AL-50-30RGBC-C-004.pdf
The Preferred Value Series Resistor on this page recommends 510/470/470 Ohms for 12VDC which to me seems too low because the maximum current is specified as 20mA per channel while Ohms law says
12V / 470 Ohms = 25.53mA
Which is above the recommended 20mA. Why is this?