What does m mean in the formula?

Question

Probability theory

There is a pseudo-random number generator, you need to statically test it using the "coupon collectors" test. This is one of Knuth's many static tests. We have the following information:

And here it says that all whip tests are based on a static criterion. However, in the line describing the "coupon collectors" test, it says that

, in accordance with this description, at the top of the page it is written that this is a test for a uniform distribution of the frequencies of occurrence of each character and the interval is given, the membership of which needs to be checked, as I understand it, instead of calculating the criterion

: does the variable m mean? Let's say I have some kind of numerical sequence, how to check its "randomness" using a given segment? What does dimension m mean?