We're dividing 399321 by 510 
The aim is to understand the frequency of 510 in 399321.

Let's proceed to step 1:
If we divide 3 by 510, we get 0 and a remainder of 3.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Subtract 0 from 3 to get 3.
Fetch the next digit (9) from the dividend, attach it to 3 and continue: 39 / 510

Moving on to step 2:
When dividing 39 by 510, we get 0 with a remainder of 39.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we subtract 0 from 39, we get 39.
Include the next digit (9) from the dividend after 39, then repeat: 399 / 510

Moving on to step 3:
399 divided by 510 is 0 with a remainder of 399.
Use 0 as the next digit of our solution. 
Result so far: 0.0
Deduct 0 from 399 and we're left with 399.
Include the next digit (3) from the dividend after 399, then repeat: 3993 / 510

Step 4:
510 goes into 3993 7 times with a remainder of 423.
The number 7 becomes the next digit in our result. 
Result so far: 7.0
Subtracting 3570 from 3993 leaves us with 423.
Include the next digit (2) from the dividend after 423, then repeat: 4232 / 510

Going ahead to step 5:
510 goes into 4232 8 times with a remainder of 152.
Record the quotient 8 as the next digit in the result. 
Result so far: 78.0
Deduct 4080 from 4232 and we're left with 152.
Bring next digit (1) of the dividend behind the 152 and repeat the process: 1521 / 510

Going ahead to step 6:
The number 510 fits into 1521 2 times, leaving a remainder of 501.
The number 2 becomes the next digit in our result. 
Result so far: 782.0
Deduct 1020 from 1521 and we're left with 501.
Since there are no more digits in the dividend, we add a zero to the remainder making it 5010, and continue the process.

Step 7:
The number 510 fits into 5010 9 times, leaving a remainder of 420.
Use 9 as the next digit of our solution. 
Result so far: 782.9
Subtracting 4590 from 5010 leaves us with 420.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4200, and continue the process.

Moving on to step 8:
The number 510 fits into 4200 8 times, leaving a remainder of 120.
Record the quotient 8 as the next digit in the result. 
Result so far: 782.98
Subtract 4080 from 4200 to get 120.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1200, and continue the process.

On to step 9:
510 goes into 1200 2 times with a remainder of 180.
The next digit of our result is 2. 
Result so far: 782.982
If we subtract 1020 from 1200, we get 180.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1800, and continue the process.

Step 10:
510 can be fit into 1800 3 times, resulting in a remainder of 270.
The number 3 becomes the next digit in our result. 
Result so far: 782.9823
Subtracting 1530 from 1800 leaves us with 270.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2700, and continue the process.

On to step 11:
The number 510 fits into 2700 5 times, leaving a remainder of 150.
Record the quotient 5 as the next digit in the result. 
Result so far: 782.98235
The remainder is 150 after subtracting 2550 from 2700.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1500, and continue the process.

Let's proceed to step 12:
The number 510 fits into 1500 2 times, leaving a remainder of 480.
Put 2 as the next digit of the answer. 
Result so far: 782.982352
If we take 1020 away from 1500, we end up with 480.
Since there are no more digits in the dividend, we add a zero to the remainder making it 4800, and continue the process.

Going ahead to step 13:
510 goes into 4800 9 times with a remainder of 210.
Record the quotient 9 as the next digit in the result. 
Result so far: 782.9823529
If we subtract 4590 from 4800, we get 210.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2100, and continue the process.

Advancing to step 14:
The number 510 fits into 2100 4 times, leaving a remainder of 60.
Write down 4 as next digit of the result. 
Result so far: 782.98235294
Subtract 2040 from 2100 to get 60.
Since there are no more digits in the dividend, we add a zero to the remainder making it 600, and continue the process.

The quotient of the division is 782.98235294, and the remainder is 6e-08.