Let's dive into this subtraction. We'll start with 613997 and subtract 99066 from it.

Step 1: We'll start by subtracting the digit 6 and the borrow 0 from 7 in column 1 and get 1.
1 is the first digit of our result.

Step 2: We'll start by subtracting the digit 6 and the borrow 0 from 9 in column 2 and get 3.
3 is the next digit of our result.

Step 3: We'll start by subtracting the digit 0 and the borrow 0 from 9 in column 3 and get 9.
9 is the next digit of our result.

Step 4: We'll start by subtracting the digit 9 and the borrow 0 from 3 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 9 and the borrow 1 from 1 in column 5 and get -9.
We add -9 to 10 and get 1 as the next digit of the result.

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

So, 613997 - 99066 = 514931.