There's no standard format that I know of--either double space, or single space with in-between para spacing. No one seems to care, really.

Have you read Donald Maass's The Career Novelist? (Free download here (http://www.maassagency.com/books.html).) I'm about halfway through, it does address synopses and says "Whatever's reasonable is okay." It also addresses quite a bit of stuff that would have been of interest to me in starting the agent search, though I was convinced the book was beyond me at that point, and put off reading it.