What’s the total number of people going to karaoke?
What are the recruitment numbers for the new Tofugu writers?
There are a great number of people who disagree with my proposal that everyone in this country must wear the same pants.
The person count is the number of people. Don't confuse this with the "population" or something like that, though. This is more like "how many people are at this event?" What's the 人数, you know?
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. Just be sure to take note of the rendaku for the second half, where すう goes to ずう.