PRNG exercises need clarification about integer representation

[terrabitz]

In the PRNG exercise, the solution is based on the following calculation, where n is the iteration number:

1 + HMAC-SHA256(n, seed) % 10

However, n can be represented a number of different ways, depending on

• Whether it should be an encoded string value (e.g. similar to the example given in https://cryptobook.nakov.com/secure-random-generators/pseudo-random-numbers-examples)
• Whether it's big or little-endian
• Whether it's signed or unsigned

When implementing the exercise, I struggled with trying a number of different representations until I finally figured out that the byte representation was supposed to be unencoded and unsigned. It might be good to include a note about this in the exercise.