Do we count… items or files or the amount of storage used?  What constitutes an item?

Do we count… master files? Derivative files? Copies on servers? Copies on tape?  Second (third, fourth) copies in other distributed preservation locations?

Do we count … files they “own?”  Have in their physical control?  License access to that lives elsewhere?

And, when they digitize one more item at 5 p.m. that hadn’t existed in their collections at 4:59 p.m., do they update their counts/extents?

So, here’s what I can say:  the Library of Congress has more than 3 petabytes of digital collections.  What else I can say with all certainty is that by the time you read this, all the numbers — counts and amount of storage — will have changed.