ODATA is Getting triggered Twice.

Hi,

We are developing Fiori apps by using SAP Standard template SAPUI5 Master Detail Templates, assign ODATA to UI5 Controls like Master List, Combo Box etc.... while testing and understanding data flow between ODATA and UI5 I noticed ODATA is getting called twice, difference between two calls IT_ORDER import parameter is filled with PROPERTY = key field Ex: ZZField1 and ORDER = asc. I can simply check and avoid one call, but I want to know the purpose of calling twice or somewhere something wrong?

Thank you !

San.