Hi,
You set capacity against a resource, e.g. Worker 1 = 8 hours a day
Working calendar is the hours in which the resource can work within, e.g. Tuesday = 8 hours, Wednesday = 8 hours.
So for example, if there's an operation that takes 16 hours, Worker 1 will be scheduled to 8 hours on Tuesday, and then complete the job with the available 8 hours on Wednesday.. abiding by the working calendar.
The working calendar is applicable to individual resources, in the example you detailed above there would never be a 40 hour day, but 5 resources with 8 hours of their own working calendar available everyday.
Once scheduled, you can check these capacity load on the resource form.
I hope this helps