Show Summary: The Snapshot summary is a high level summary of the key takeaways from your report. This summary is automatically calculated if you select show summary.
Display Legend: The display legend checkbox gives you the option to either, display at the top of the report the completion status legend, or not at all.
Sort By: You can also determine how your Goals are sorted. Goals can be sorted by Title, Completion, Start Date, Due Date, Status, Owner, Organization, Focus Area, Templates, and any of your added Custom Fields. Basically, you can sort your Snapshot results any way that you need. You can also sort on multiple levels, for example, you could do your first level of sorting by Owner, and your second by Due Date.
Export Font Size: If you'll be exporting the report to a PDF, you have an option to determine the font size that will be used in the PDF download. Note: this won't change the size of the font on the report in Cascade, only in the PDF.