<?xml version="1.0" encoding="UTF-8"?>
<form>
    <fieldset name="basic">
        <field name="gap" type="nrnumber"
            label="COM_CONVERTFORMS_FIELD_EMPTY_SPACE_GAP"
            description="COM_CONVERTFORMS_FIELD_EMPTY_SPACE_GAP_DESC"
            addon="px"
            min="0"
            default="20"
        />
    </fieldset>
</form>