In Settings user form i need on drop down box, based on groups, in that dropdown i need 7 type of users but i can add ony 3 users only, if i added 4 th user means it go to a check box. how to solve this. Here is my sample code.

<record model="ir.module.category" id="module_category_branch_management">
            <field name="name">Plant</field>
            <field name="description">Plant Management</field>
            <field name="sequence">20</field>            
    </record>

    <record id="group_uk_branch_user" model="res.groups">
        <field name="name">Branch User</field>        
    </record>

    <record id="group_uk_user" model="res.groups">
        <field name="name">UK</field>
        <field name="category_id" ref="module_category_branch_management"/>
        <field name="implied_ids" eval="[(4, ref('group_uk_branch_user'))]"/>
    </record>

    <record id="group_usa_user" model="res.groups">
        <field name="name">USA</field>
        <field name="category_id" ref="module_category_branch_management"/>
        <field name="implied_ids" eval="[(4, ref('group_uk_branch_user'))]"/>
    </record>

    <record id="group_uae_user" model="res.groups">
        <field name="name">UAE</field>
        <field name="category_id" ref="module_category_branch_management"/>
        <field name="implied_ids" eval="[(4, ref('group_uk_branch_user'))]"/>
    </record>

    <record id="group_ind_user" model="res.groups">
        <field name="name">IND</field>
        <field name="category_id" ref="module_category_branch_management"/>
        <field name="implied_ids" eval="[(4, ref('group_uk_branch_user'))]"/>
    </record>