OK, let's do this. We've got 411015 and 10420, and we're subtracting the second number from the first.

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

Step 2: We'll start by subtracting the digit 2 and the borrow 0 from 1 in column 2 and get -1.
We add -1 to 10 and get 9 as the next digit of the result.

Step 3: We'll start by subtracting the digit 4 and the borrow 1 from 0 in column 3 and get -5.
We add -5 to 10 and get 5 as the next digit of the result.

Step 4: We'll start by subtracting the digit 0 and the borrow 1 from 1 in column 4 and get 0.
0 is the next digit of our result.

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

Step 6: We'll start by subtracting the digit 0 and the borrow 0 from 4 in column 6 and get 4.
4 is the next digit of our result.

So, 411015 - 10420 = 400595.