No no, you do have to understand how the RNG system works. RNG system is NOT like throwing a dice. it's NOT picking a random number from the pool every time. That would be a true RNG or whatever else is called.

Now I do not feel like making a whole post, because nobody will read that anywyas

But in very short version, RNG uses a seed (often server sided, but does not have to be) and adds or subtracts from that seed.

So let's assume you have scale from 0 - 300 (this is just an example, do not quote any numbers) and 6 letters so letter N is from 0 - 50, A 51-100 etc.
In this case when you pull 10 and assume your seed is 67 you will get a lot of N's, A's, R's but getting O's will be unlikely with that current seed.

Usually seeds change after some period of time, but that c*l be very different in each instance of that system, so I'll skip that part.

Of course it is possible to write the system for one letter to have a smaller pool of numbers, but that would be very visible, as the same letter would be missing for a most of the players, which is not the case.


TL: DR - RNG used in 99,95% of games and instances is very imperfect system, that punishes (or rewards) you for using it in quick succession depending on the current seed.