What is the logic of 1 to be here

#1

i mean what this 1 represent and how in terms of its children , please don’t tell me the formula i know it , just make me understand how it came via example !!

#2

image

#3

same for 0 , the answer is 2 , so please also tell that as well

#4

I just need to understand for 2 subtrees of bigger size that is one rooted at 1 and other at 0