@ Andy Cool yes you have got it.
@ dhenry
I will make it simpler for you: what is Vfwd when If = 0, for any led / diode of your choice?
The Vfwd is what the manufacturer states
the forward voltage accross the LEDs is 5v , they have not reached their combined series Vf of 6 volts yet.
The voltage accross the resistor is zero, so no current.
Try it with a meter the voltage accross the LEDs will be 5v.