Not understanding why a transition isn't working in Node red

Trying something very simple where the bulb slowly comes on.
In node red for test I have

The first set, brightness to 10 and white_value to 10 to make sure the bulb is at low brightness
Next I wait for 10 seconds to make sure HA has received the change.
Last is I set white_value to 255 and transition of 20

I find that in this case the bulb never does the transition and stays at a white_value, if on the other hand I go straight to the transition it works fine.

So how can I set the light to do a slow turn on, if I can’t set the starting value?