OK, let's do this. We've got 66539 and 6533, and we're subtracting the second number from the first.

Step 1: We'll start by subtracting the digit 3 and the borrow 0 from 9 in column 1 and get 6.
6 is the first digit of our result.

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

Step 3: We'll start by subtracting the digit 5 and the borrow 0 from 5 in column 3 and get 0.
0 is the next digit of our result.

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

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

So, 66539 - 6533 = 60006.