We look at the division of 25621 by 78 
The aim is to understand the frequency of 78 in 25621.

Advancing to step 1:
If we divide 2 by 78, we get 0 and a remainder of 2.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
The remainder is 2 after subtracting 0 from 2.
Include the next digit (5) from the dividend after 2, then repeat: 25 / 78

Step 2:
The number 78 fits into 25 0 times, leaving a remainder of 25.
The next digit of our result is 0. 
Result so far: 0.0
Subtracting 0 from 25 leaves us with 25.
Append the next digit (6) from the dividend to 25 and continue with: 256 / 78

Step 3:
256 divided by 78 is 3 with a remainder of 22.
Record the quotient 3 as the next digit in the result. 
Result so far: 3.0
If we subtract 234 from 256, we get 22.
Append the next digit (2) from the dividend to 22 and continue with: 222 / 78

Moving on to step 4:
When dividing 222 by 78, we get 2 with a remainder of 66.
Use 2 as the next digit of our solution. 
Result so far: 32.0
If we take 156 away from 222, we end up with 66.
Include the next digit (1) from the dividend after 66, then repeat: 661 / 78

Moving on to step 5:
The number 78 fits into 661 8 times, leaving a remainder of 37.
The number 8 becomes the next digit in our result. 
Result so far: 328.0
If we take 624 away from 661, we end up with 37.
Since there are no more digits in the dividend, we add a zero to the remainder making it 370, and continue the process.

Step 6:
78 goes into 370 4 times with a remainder of 58.
The number 4 becomes the next digit in our result. 
Result so far: 328.4
The remainder is 58 after subtracting 312 from 370.
Since there are no more digits in the dividend, we add a zero to the remainder making it 580, and continue the process.

Moving on to step 7:
If we divide 580 by 78, we get 7 and a remainder of 34.
The next digit of our result is 7. 
Result so far: 328.47
If we take 546 away from 580, we end up with 34.
Since there are no more digits in the dividend, we add a zero to the remainder making it 340, and continue the process.

On to step 8:
78 goes into 340 4 times with a remainder of 28.
The next digit of our result is 4. 
Result so far: 328.474
Subtracting 312 from 340 leaves us with 28.
Since there are no more digits in the dividend, we add a zero to the remainder making it 280, and continue the process.

Going ahead to step 9:
280 divided by 78 is 3 with a remainder of 46.
Use 3 as the next digit of our solution. 
Result so far: 328.4743
If we subtract 234 from 280, we get 46.
Since there are no more digits in the dividend, we add a zero to the remainder making it 460, and continue the process.

Let's proceed to step 10:
When dividing 460 by 78, we get 5 with a remainder of 70.
Use 5 as the next digit of our solution. 
Result so far: 328.47435
The remainder is 70 after subtracting 390 from 460.
Since there are no more digits in the dividend, we add a zero to the remainder making it 700, and continue the process.

Let's proceed to step 11:
700 divided by 78 is 8 with a remainder of 76.
Write down 8 as next digit of the result. 
Result so far: 328.474358
Subtract 624 from 700 to get 76.
Since there are no more digits in the dividend, we add a zero to the remainder making it 760, and continue the process.

Advancing to step 12:
78 can be fit into 760 9 times, resulting in a remainder of 58.
The next digit of our result is 9. 
Result so far: 328.4743589
Subtract 702 from 760 to get 58.
Since there are no more digits in the dividend, we add a zero to the remainder making it 580, and continue the process.

Step 13:
The number 78 fits into 580 7 times, leaving a remainder of 34.
Record the quotient 7 as the next digit in the result. 
Result so far: 328.47435897
The remainder is 34 after subtracting 546 from 580.
Since there are no more digits in the dividend, we add a zero to the remainder making it 340, and continue the process.

After the division, we end up with 328.47435897 and a remainder of 3.4e-08.