odoo-pos-addons/pos_restaurant_table_booking/models/res_config_settings.py

# -*- coding: utf-8 -*-
from odoo import models, fields


class ResConfigSettings(models.TransientModel):
    _inherit = 'res.config.settings'

    default_duration = fields.Float(string="Default duration", default_model='restaurant.booking')

    _sql_constraints = [
        ('duration_positive', 'CHECK(default_duration >= 0)', "The default booking duration must be positive or null.")
    ]