In file Start 2.1.yxdb we have below record with annual transaction value of 86:
In file Start 2.2.yxdb we have below record with annual transaction value of 100:
When you eliminate duplicate using Cutomer_ID & Customer_Segment we loosing a real transaction worth 100 and 86 goes into output which I believe is wrong. After Union we must SUMMARIZE to get a value of 186.