Solution to problem 2 option d

In the solution to the problem 2d, I've not understood what does it mean the sum of the combinations. The result 792 does already include all possible combinations with repetition, for example 2 times banner 1, 1 time banner 4 and 2 times banner 7; or 3 times banner 2, 1 time banner 6 and 1 time banner 8. So what represents the sum of combinations written below and why "it is vital to not only know which banners we are using, but also to know how many times we are using each one"? Thank you