That might be intended for a pulsed configuration, where the led is controlled by a square wave with a frequency and duty cycle that overdrives the LED for a fraction of the second, then turns it off before it heats itself up enough to cause damage. The frequency is set to a rate that makes the LED appear to be continuously on to the human eye, I think thats around 60Hz+
1mA just sounds low to me, but it's your LED, I'll take your word for it. Just check the datasheet for stipulations of duty cycle, frequency, and peak current near that 5mW rating.