Understanding the start render

[nemlah]

Hello,
We are plotting start render and first paint for some of our pages and I have noticed that huge DOM pages (~20k nodes) show a strong difference between start render vs first paint whereas pages with a normal DOM size show almost no difference.
As I understand it and given the actual name of the metrics, start render is the beginning of the render phase when CSSOM and the DOM are combined into the render tree, whereas the first paint happens after the render tree and layout stage when the browser actually paints something on the screen.

Can someone clarify/confirm the above?

Thanks