Got it! So, we have 6604 and 2289, and we'll subtract the latter from the former.

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

Step 2: We'll start by subtracting the digit 8 and the borrow 1 from 0 in column 2 and get -9.
We add -9 to 10 and get 1 as the next digit of the result.

Step 3: We'll start by subtracting the digit 2 and the borrow 1 from 6 in column 3 and get 3.
3 is the next digit of our result.

Step 4: We'll start by subtracting the digit 2 and the borrow 0 from 6 in column 4 and get 4.
4 is the next digit of our result.

So, 6604 - 2289 = 4315.