How does the Business Decimal Days calculation occur?

This use case is described based on the 8/5 calendar, which is shown below.

Choose this calendar from the drop-down list directly in the add-on:

Now the calculation for all issues will be according to the chosen calendar.

When you choose Days, the calculation occurs according to the hours in a calendar day (24h):

8h / 24h = 0.33d

So, the task was in active statuses for 0.33d (during the working day).

If you need to get data based ONLY on the working hours (for example, 8 hours), you need to choose the Business Decimal Days. It turns out that 8 working hours is your whole working day. So, the calculation occurs in such a way: 8h/8h = 1d.