Hi luis, thank you for your PM!
As said in the walkthrough you need to work out the numbers that correspond to the letters in the words ‘MODIFY GRADES’.
You only need to choose words that use the letters in ‘MODIFY GRADES’ i.e. M, O , D etc
To determine which numbers correspond to the letters, you have to split the sequence of numbers into four parts for each four-letter word. Use subsequent words to help identify the code for a specific letter. It helps to try pinpointing one letter to start with e.g. M
In the example in the walkthrough the word MODE gives you the sequence 93558248350316 so M=9 or 93 or 935 or 9355
Typing in the word MAID next gives you the sequence 9355353503 but that’s still not enough info.
FARM gives you the sequence 5638019355 so as you already know that M starts with 9 the code for M must be 9355. Once you’ve worked out the code for one letter you can then work out the code more easily for other letters.
MODE 9355(M) - 8248350316(ODE)
MAID 9355(M) - 3(A) - 53503(ID)
FARM 56 -3 -801(FAR) - 9355(M)
You can now work out that A = 3 & F = 56.
I don’t how well I’ve explained this but if it hasn't made any sense please ask more if you need to.
You need a lot of concentration & to take your time with this puzzle.
I may have a saved game if you're really desperate