你的同事在 Display & Video 360 為客戶的行動網路廣告活動建立委刊項時，不小心將行動應用程式內廣告設為指定目標。他們隨後在廣告訂單層級移除了指定的行動應用程式內廣告，但廣告活動的指定目標還是行動應用程式內廣告。 請問為什麼會出現這種情況？

The correct answer is that you cannot modify existing line item targeting at the insertion order level. In Display & Video 360, targeting settings are hierarchical. While you can set targeting at the insertion order level, these settings act as a default or a filter for new line items created under that insertion order. Once a line item is created, its specific targeting settings are managed at the line item level. Changes made to targeting at the insertion order level will not override or modify the targeting of existing line items. Therefore, even though the mobile in-app targeting was removed at the insertion order level, the line item retained its original mobile in-app targeting because it was already established. To correct the targeting, the colleague needs to directly edit the line item's targeting settings.