半年之前发生的问题，今天看到凭证小记一笔， 问题来源于外币采购一笔材料，材料以移动平均价管理，同一个PO做了两笔IR, 而且两次的汇率不一样（一个是维护了当日汇率之前做的，一个是维护了当日汇率之后做的）。

PO HISTORY:

1,IR(DR:GR/IR; CR:AP) 7.60030    30781.22    4050    07.08.20 09:32:51    07.08.20(Pst.Dt.)
2,IR(DR:GR/IR; CR:AP) 7.59730    30769.07    4050    07.08.20 09:44:36    07.08.20(Pst.Dt.)
3,GR(DR:MAT;CR:GR/IR) 7.59730    30775.15    4050    07.08.21 09:25:20    07.08.21(Pst.Dt.)
4,IR(DR:AP; CR:GR/IR) 7.60030    -30781.22    4050    07.08.30 09:35:07    07.08.20(Pst.Dt.)
    
从上面可以看出材料的入库金额是以IR的金额为准的，而且取了个中间数（哪里配置GR的时候的价值以哪个为基准呢？）
    4 为cancel第一笔IR，对应的FI凭证中的CNY金额是30775.15（既没有取7.59730也没有取7.60030） 同时入差异-6.08到成本变动逆差科目（PRD）


关于PRD：

• Price differences (PRD)

Price differences arise for materials valuated at standard price in the case of all movements and invoices with a value that differs from the standard price. Examples: goods receipts against purchase orders (if the PO price differs from the standard pricedardpreis), goods issues in respect of which an external amount is entered, invoices (if the invoice price differs from the PO price and the standard price).

Price differences can also arise in the case of materials with moving average price if there is not enough stock to cover the invoiced quantity. In the case of goods movements in the negative range, the moving average price is not changed. Instead, any price differences arising are posted to a price difference account.

Depending on the settings for the posting rules for transaction/event key PRD, it is possible to work with or without account modification. If you use account modification, the following modifications are available in the standard system:

• None for goods and invoice receipts against purchase orders
• PRF for goods receipts against production orders and
  order settlement
• PRA for goods issues and other movements
• PRU for transfer postings (price differences in the case
  of external amounts)