I did a really simple setup try to study how blend work in gas calculate. Here is an empty dop initialize with fix density value 2, then solve on creation frame to compute gas calculate just once. I got no idea why the density sum up to 16.

here is what I calculate according to reference card, but the value doesn't add up.

dest = density = 2
dest process = dest + dest pre-add = 2 + 5 = 7
source process = source + source pre-add = 0 + 2 = 2

dest blend process = 1
source blend process = 1

blend mode weightSum = dest process * dest blend process + source process * source blend porcess = 7 * 1 + 2 * 1 = 9

9 is what I get

In help card ‘Blend Method’ parameter, it mention “The destination and source blend fields are used to blend the result of the gas calculation onto the destination field.” But I have not pick up any relevant blend method formula listed blow dress what's mention.

It must be something I didn't realize. Could anybody shed some light please