Last year Nepal was held 9500. You don't add them together, the 9500 is included in the 13350 number - meaning that although the numbers rose past 9500 for other countries in Asia, Nepal cases were not scheduled past 9500.
Also. Each case number includes derivatives, BUT not all case numbers are real numbers - some are gaps. So you could see something like this:-
Case Number - number of visas(selectees plus Family)
1 - 3
2 - 1
4 - 7
6 - 1
Notice the gaps - we call those "holes". And the column is how many "selectees" are attached to each number.
This is explained in detail here:
http://britsimonsays.com/the-lottery-draw-process-holes-theory-and-so-on/