Answer:
The second half of the sentence, the number of available jobs is going up—quickly, should be emphasized to best convey meaning.
Step-by-step explanation:
The sentence Something else important about the numbers involved in video games: the number of available jobs is going up—quickly, is divided in to two parts as can be seen. The first part of the sentence 'Something else important about the numbers involved in video games' gives a clue to a piece of information, while the second half of the sentence 'the number of available jobs is going up—quickly' tells us what that information is.
To best convey meaning of the whole sentence the second part should be emphasized, as the first part makes sense because of it.