Hi,

To add default value in res.config.settings,

Inside your module create a data file as follows

<?xmlversion="1.0" encoding="utf-8"?>

<odoo>

    <!-- Adding adefault value for field_name in res.config.settings-->

    <datanoupdate="1">

        <recordid="test_view" model="ir.config_parameter">

            <fieldname="key">module_name. field_name</field>

            <fieldname="value">80</field>

        </record>

    </data>

</odoo>

Hope it helps