Substitute and Array Function

Hi there, I'd like to know how the formula below is equal to the anwer below?

I'm not sure what the Substitute function does in the query below? I know the outer query is an array.

Problem:

Value of G2: 179736

Formula: =SUM((LEN(SUBSTITUTE(G2,{1,2,3,4,5,6,7,8,9},"")))*{1,2,3,4,5,6,7,8,9})

Answer: 237

It takes number 179736 and then replace every number with nothing and look LEN of it:

Number 1 (79736) ---> 5
Number 2 (179736) ---> 6
Number 3 (17976) ---> 5
Number 4 (179736) ---> 6
Number 5 (179736) ---> 6
Number 6 (17973) ---> 5
Number 7 (1936) ---> 4
Number 8 (179736) ---> 6
Number 9 (17736) ---> 5

Then it multiply it with numbers 1,2,3 etc

(5,6,5,6,6,5,4,6,5) * (1,2,3,4,5,6,7,8,9)
=(5,12,15,24,30,30,28,48,45)

And SUM it 237

Thank you so much!!!! And thanx for the nice explanation!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!