tra_backend/ohrms_overtime/views/hr_contract.xml

<odoo>
    <data>
        <record model="ir.ui.view" id="hr_contract_overtime_view">
            <field name="name">hr.contract.overtime.form.inherit.view</field>
            <field name="model">hr.contract</field>
            <field name="inherit_id" ref="hr_contract.hr_contract_view_form"/>
            <field name="arch" type="xml">
                <xpath expr="//group[@name='allowances']" position="after">
                    <group string="Overtime">
                        <label for="over_day"/>
                        <div class="o_row" name="day_wage">
                            <field name="over_day"/>
                            <span>/day</span>
                        </div>
                        <label for="over_hour"/>
                        <div class="o_row" name="hour_wage">
                            <field name="over_hour"/>
                            <span>/hour</span>
                        </div>
                    </group>
                </xpath>
            </field>
        </record>
    </data>
</odoo>