Hi,
If you are looking to include the leave days in the time off request, you need to modify the function _get_number_of_days in the model hr.leave .

Inherit the model and rewrite the corresponding function like this, and make sure it will not make error in other existing functionalities.

from odoo.addons.resource.models.resource import float_to_time, HOURS_PER_DAY


class HolidaysRequest(models.Model):
    _inherit = "hr.leave"

    def _get_number_of_days(self, date_from, date_to, employee_id):
        days = (date_to - date_from).days
        return {'days': days, 'hours': HOURS_PER_DAY * days}

Thanks