英语翻译The advance payment shall be credited against the first

英语翻译
The advance payment shall be credited against the first payment to be made by the purchaser in consideration for UIBFR delivered until the total amount of the advance payment has been taken into account;
同时还有这句
The advance payment shall be credited against the first payment to be made by the purchaser in consideration for UIBFR delivered on a pro rata basis until the total amount of the advance payment has been taken into account;