I would think a simple smart list could get you the count and/or list:
Smart list:
Use Advanced Filters 1 AND (2 OR 3)
1. Visited web page: Is Any;
Date of Activity: Between (list your dates)
2. Is anonymous: True
3. Is anonymous: False
If you omit the two Anonymous filters, you'll only get known leads that have been tagged (visited a web page or clicked on a link in a Marketo email).