Calculate minimum voltage to turn off/on solid state relay
The IfOn Max current is the current that the least sensitive relay should require to turn in - most will turn on at lower currents, but you should supply at least 3 mA to ensure that any relay will be on.  The Ablosute Maximum LED current is 50 mA, so it is safe to supply more than 3 mA.

For turn-off, there is IfOff Minimum of 0.4 mA - most units will turn off at a higher current, but the most sensitive may stay on with currents as low as 0.4 mA, so you should ensure that the LED current is below 0.4 mA when you want the thing to be off.