The RunLog Statistics window allows you to view Daily, Weekly, and Monthly Minimum, Average, and Maximum Distance, Time, Pace and number of runs for any time period.

RunLog gives you a bunch of standard date ranges and also lets you enter your own range. Year to date takes all your runs from Jan 1 of the selected year to the current date. You can also select "Entire Year" (Jan 1-Dec 31), or a specific month from the Month field, and select a specific year or "All Years" in the Year field. You can also choose "Date Range" and enter any 2 dates you want.

It's easiest way to describe the statistics is if I give you an example. So, taking the window below, I'll describe the Weekly Distance numbers. You should be able to figure the rest out from that. Since "Year to date" is selected, all these numbers mean: From the beginning of the year... Minimum: The shortest I ran in a week is 13.4 miles, Average: My Average week was 37.2 miles, and Maximum: The most I ran in a week is 43.85 miles.  

You can also pick any 2 User Defined Fields to display: