Solution

Go to Time Off App > Configuration > Accrual Plans, and click on "New".

Important Notes: 

• To base the accrual plan on worked time the accrued gain time must be "At the end of the accrual period".
• The company wants to carry the days left to the next calendar year so, we should select the value "At the start of the year" in the field Carry-Over Time.
• Check the Based on Worked  Time Field  

Now let's go configure the Rules: 

The employee accrues .057 Days per hour. Once we select that the employee accrues hourly Odoo will display a field "Source". In this field, we select if we want the work time to be based on working schedule or attendance records. 

Then check  "Cap accrued time" and add 15 days (Because that is the maximum that an employee could accrue). To start the plan immediately add 0 days in the field "Milestone reached" and to carry over a maximum of 7 days to the next year select the option "Carry Over with a maximum" and add 7.

So we have finished the accrual plan configuration! 

Now what you need to do is to allocate the accrual plan!

Good Luck!