BigPicture and FTE management

[Deleted user]

To summarise, I am trying to understand if and how it is possible to use BigPicture to represent a person's commitment based on an activity that lasts a certain number of days per month. Let me explain myself a little better. Imagine a customer says to us: I want to buy 10 days of system support per month. What that means to me is that I have Team A, for example, potentially busy with one person for 10 days a month. At the moment I have a rough idea of who I want to assign the task to. And I do that by creating a single task, one per month, twelve tasks in total, of the duration of the month (so start date is day 1 of the month and end date is the 30th of the month, let's say). Then I set an initial estimate equal to 10 days of work. I would like to know if this way of setting up is correct or do you have a better suggestion to do with BigPicture. Thank you for your attention.

The problem arises when I then have to assign individual tasks to the person (these are the sub-tasks of the first monthly task) that explain the specific intervention that is done on a certain day within the 10-day commitment month. The original estimate work hours of the sub-task would be added to the work hours of the main task. And this is no good.