Alright, ready to do some subtraction? We're taking 994900 and subtracting 4387 from it.

Step 1: We'll start by subtracting the digit 7 and the borrow 0 from 0 in column 1 and get -7.
We add -7 to 10 and get 3 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 3 and the borrow 1 from 9 in column 3 and get 5.
5 is the next digit of our result.

Step 4: We'll start by subtracting the digit 4 and the borrow 0 from 4 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 9 in column 5 and get 9.
9 is the next digit of our result.

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

So, 994900 - 4387 = 990513.