Confusing question.
Non-Working time is the time a task is not working: week ends, nights...
Availability would be when a resource is available to work.
A resource may be available 7 days a week but the task may only need to work
6 days a week to complete on time. In this case the task will work 6 days a
week.
Or a task may need to work 7 days a week to complete on time, but the
resources are only available 5 days a week. In this case the task will only
work 5 days a week.
Although the MSP group don't agree with what I am about to say: I make my
resource available 7 days a week and 24 hours a day. This allows me to use
the task calendar to set the working time. Keep in mind I only work on outage
schedules. Confusing answer??