This question is about the previously answered question
Proof that there are infinitely many prime numbers starting with a given digit string
What I dont understand about the question is how the number of beginning digits is related to the value n (referring to the answer by A. Nicholas). n will determine the length of the primes that starts with 324 (in hexadecimal). Lets refer to the length of the beginning digits as L. So for the case 324 then L=3. So my question is what is the formula that gives the bounds of n (or exact value of n) given L?