on the top of的意思是:在……上面,在……顶端,
例如:The lamp is on top of the table. 灯在桌子上方。
on top of 也有在……上面的意思,同时还有“除此之外”的意思,
例如:the lamp is on top of the table. 灯在桌子上方。
on top of all the costs, you'll have to pay an extra of 15% service charge. 除了以上所有费用,你还要支付另外15%的服务费。
参考资料:http://zhidao.baidu.com/question/141804942.html