请问这是什么？为什么要三种？？

我厂有一批货要出口到南非。然后我问客人清关的文件需要什么？ 客人回我：please note we require the following invoices: 1). commercial invoice showing 100 % f.o.b value 2). commercial invoice showing 85% of the f.o.b value 3). commercial invoice showing 15% of the f.o.b value with the wording: “invoice in respect of procurement commission for goods sold to interbrand”. this invoice to he “a” after the invoice number. 4). invoice from a third party company, as proof that the goods are manufactured by a third party factory. this invoice to be at the 85% value, with different date and invoice number. 5). invoice the 85% value in zar currency, since we clear in the local currency through customs. please insert the wording: “ we confirm that there are various fec contracts purchased for the period 30th june 2013 to 30th june 2014. the rate used is 9.20. we confirm that the us $ amount is ………. 6). packing list, showing style number, quantity and colour per carton packed. 为什么会有三种，另外，为什么要加一些句子， wording: “invoice in respect of procurement commission for goods sold to interbrand”. this invoice to he “a” after the invoice number. 和insert the wording: “ we confirm that there are various fec contracts purchased for the period 30th june 2013 to 30th june 2014. the rate used is 9.20. we confirm that the us $ amount is ………. 我之前没有遇到这样的。 请教一下大家。