If a user views an article HTML and then downloads the PDF in the same session, how do you count this usage?

If this activity happened in less than 30 seconds then it will be counted as:

Unique_Item_Requests = 1
Total_Item_Requests = 1
Unique_Item_Investigations = 1
Total_Item_Investigations = 1

If this activity happened in more than 30 seconds then it will be counted as:

Unique_Item_Requests = 1
Total_Item_Requests = 2
Unique_Item_Investigations = 1
Total_Item_Investigations = 2