30359858 ÷ 399 
The aim is to understand the frequency of 399 in 30359858.

Advancing to step 1:
If we divide 3 by 399, we get 0 and a remainder of 3.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtracting 0 from 3 leaves us with 3.
Bring next digit (0) of the dividend behind the 3 and repeat the process: 30 / 399

Advancing to step 2:
399 goes into 30 0 times with a remainder of 30.
The next digit of our result is 0. 
Result so far: 0.0
Deduct 0 from 30 and we're left with 30.
Include the next digit (3) from the dividend after 30, then repeat: 303 / 399

Moving on to step 3:
If we divide 303 by 399, we get 0 and a remainder of 303.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
Subtract 0 from 303 to get 303.
Take the next digit (5) from the dividend and append it to 303, then repeat: 3035 / 399

Advancing to step 4:
399 can be fit into 3035 7 times, resulting in a remainder of 242.
The next digit of our result is 7. 
Result so far: 7.0
Subtract 2793 from 3035 to get 242.
Fetch the next digit (9) from the dividend, attach it to 242 and continue: 2429 / 399

Going ahead to step 5:
The number 399 fits into 2429 6 times, leaving a remainder of 35.
Put 6 as the next digit of the answer. 
Result so far: 76.0
Deduct 2394 from 2429 and we're left with 35.
Fetch the next digit (8) from the dividend, attach it to 35 and continue: 358 / 399

Moving on to step 6:
When dividing 358 by 399, we get 0 with a remainder of 358.
The number 0 becomes the next digit in our result. 
Result so far: 760.0
Subtract 0 from 358 to get 358.
Fetch the next digit (5) from the dividend, attach it to 358 and continue: 3585 / 399

Moving on to step 7:
The number 399 fits into 3585 8 times, leaving a remainder of 393.
Put 8 as the next digit of the answer. 
Result so far: 7608.0
Subtract 3192 from 3585 to get 393.
Include the next digit (8) from the dividend after 393, then repeat: 3938 / 399

Moving on to step 8:
399 can be fit into 3938 9 times, resulting in a remainder of 347.
Record the quotient 9 as the next digit in the result. 
Result so far: 76089.0
The remainder is 347 after subtracting 3591 from 3938.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3470, and continue the process.

Step 9:
The number 399 fits into 3470 8 times, leaving a remainder of 278.
The number 8 becomes the next digit in our result. 
Result so far: 76089.8
Deduct 3192 from 3470 and we're left with 278.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2780, and continue the process.

Advancing to step 10:
If we divide 2780 by 399, we get 6 and a remainder of 386.
The next digit of our result is 6. 
Result so far: 76089.86
The remainder is 386 after subtracting 2394 from 2780.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3860, and continue the process.

On to step 11:
The number 399 fits into 3860 9 times, leaving a remainder of 269.
Put 9 as the next digit of the answer. 
Result so far: 76089.869
Subtract 3591 from 3860 to get 269.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2690, and continue the process.

Let's proceed to step 12:
The number 399 fits into 2690 6 times, leaving a remainder of 296.
Write down 6 as next digit of the result. 
Result so far: 76089.8696
If we subtract 2394 from 2690, we get 296.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2960, and continue the process.

Advancing to step 13:
399 goes into 2960 7 times with a remainder of 167.
The number 7 becomes the next digit in our result. 
Result so far: 76089.86967
Subtracting 2793 from 2960 leaves us with 167.
Since there are no more digits in the dividend, we add a zero to the remainder making it 1670, and continue the process.

Step 14:
1670 divided by 399 is 4 with a remainder of 74.
The next digit of our result is 4. 
Result so far: 76089.869674
If we take 1596 away from 1670, we end up with 74.
Since there are no more digits in the dividend, we add a zero to the remainder making it 740, and continue the process.

Let's proceed to step 15:
399 goes into 740 1 times with a remainder of 341.
The number 1 becomes the next digit in our result. 
Result so far: 76089.8696741
Deduct 399 from 740 and we're left with 341.
Since there are no more digits in the dividend, we add a zero to the remainder making it 3410, and continue the process.

Step 16:
When dividing 3410 by 399, we get 8 with a remainder of 218.
Write down 8 as next digit of the result. 
Result so far: 76089.86967418
Subtracting 3192 from 3410 leaves us with 218.
Since there are no more digits in the dividend, we add a zero to the remainder making it 2180, and continue the process.

The final outcome is 76089.86967418, with a leftover of 2.18e-07.