Got it! So, we have 662790 and 8437, and we'll subtract the latter from the former.

Step 1: We'll start by subtracting the digit 7 and the borrow 0 from 0 in column 1 and get -7.
We add -7 to 10 and get 3 as the first digit of the result.

Step 2: We'll start by subtracting the digit 3 and the borrow 1 from 9 in column 2 and get 5.
5 is the next digit of our result.

Step 3: We'll start by subtracting the digit 4 and the borrow 0 from 7 in column 3 and get 3.
3 is the next digit of our result.

Step 4: We'll start by subtracting the digit 8 and the borrow 0 from 2 in column 4 and get -6.
We add -6 to 10 and get 4 as the next digit of the result.

Step 5: We'll start by subtracting the digit 0 and the borrow 1 from 6 in column 5 and get 5.
5 is the next digit of our result.

Step 6: We'll start by subtracting the digit 0 and the borrow 0 from 6 in column 6 and get 6.
6 is the next digit of our result.

So, 662790 - 8437 = 654353.