The only only problem with that estimation is that with only 6 trains total, the total cycle time would have to be 3 minutes long to maintain 30 second dispatches. Take out a minute each for unload & load, and that leaves 1 minute of ride time.The capacity math is a little more complicated than that - it requires something to account for the ride time or the dispatch interval.
If we make a conservative estimate of 6 trains on track at a time with one dispatching every 30 seconds, the hourly capacity would be 1680 people per hour. This would imply that most of the ride is relatively fast moving - if more of it is slow and there are more blocks then there could be more trains running at once and a longer ride time.