Auto Log Off functionality

My organiztion is in the process of extending EPDM to the Sales and Marketing division. I plan on using the Viewer licenses for the sales group and currently using Contributor license for the Marketing group (authors of product documentation).

My question is this:

When using the auto log off function what is the real definition of "inactivity" in the Admin documentation? Is this computer "inactivity" or inactivitiy of the user to access documents\\searches inside of EPDM? This will make a huge difference in the amount of license I need to purchase for the Sales group.

Currently running EPDM 2011 and moving to 2013 SP3 in the next quarter.

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