Got it! So, we have 4391 and 1781, and we'll subtract the latter from the former.

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

Step 2: We'll start by subtracting the digit 8 and the borrow 0 from 9 in column 2 and get 1.
1 is the next digit of our result.

Step 3: We'll start by subtracting the digit 7 and the borrow 0 from 3 in column 3 and get -4.
We add -4 to 10 and get 6 as the next digit of the result.

Step 4: We'll start by subtracting the digit 1 and the borrow 1 from 4 in column 4 and get 2.
2 is the next digit of our result.

So, 4391 - 1781 = 2610.