求教L/C条款

     最近谈了个乌克兰的新客人，要下一个40‘柜的货，付款方式是信用证，一开始客人说他要开： unconfirmed irrevocable L/C at sight; 本来是请客人能否改为开立“confirmed irrevocable L/C at sight”，客人不同意，回复如下：

we'll use "covered unconfirmed irrevocable L/C at sight":

- covered: means that our money for 100% amount will be reserved at Ukrainian Bank since the 1-st date of L/C;

- unconfirmed: means that there is only one Bank  in Ukraine guarantees to arrange the payment after you provide all the docs;

- confirmed: means that there is a Ukrainian bank and one more Bank that guarantees the payment to you;

We don't speciy the word "covered" in the Contrcat during the description of L/C. In case of need we'll revise it and you will be sure that 100% amount is reserved at our Ukrainian Bank.

我google了下，没找到“"covered unconfirmed irrevocable L/C at sight"”这个代表什么意思，万能的米课小伙伴，有懂的么，求教，谢谢