Let's get this math done. We have 859999 and 3623, and we're going to subtract 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 2 and the borrow 0 from 9 in column 2 and get 7.
7 is the next digit of our result.

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

Step 4: We'll start by subtracting the digit 3 and the borrow 0 from 9 in column 4 and get 6.
6 is the next digit of our result.

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

Step 6: We'll start by subtracting the digit 0 and the borrow 0 from 8 in column 6 and get 8.
8 is the next digit of our result.

So, 859999 - 3623 = 856376.