I need some help in understanding the equations involved in finding the index of an element in an ndarray. I have been reading the Book “Guide to NumPy” by Travis A Oliphant. The link to that books is given below.text

On page number number 28 of the book, Travis has given some equations, which, If I am understanding correctly is a formula to calculate index of an element(of an array stored on a storage medium) in a multidimensional array in both C-style and Fortran-Style. I am not able to get my head around that formula. The example that he has given is also not making much of a sense. I am pasting the image of that formula below, but if its not too much to ask you can even go to that link of his book and scroll to the page 28.

Any help in understanding it would be highly appreciated. enter image description here

I tried to do research on the available sources online and also tried to understand the meaning behind the mathematical notations used in the equation, but the description is not very clear. Besides there is not much help available on these equations anywhere.