Hi Sarah,
First, a couple things that might help in general. I'm sure you've seen our documentation, but here's a link to some tips on preparing descriptions for CSV import:
We also have some slides from our Camps that you might find more accessible than a lot of text:
They only have a few rows of placeholder sample data, much of which doesn't really reflect real archival description, but you still might find it helpful to take a look at the CSV templates we keep on our wiki - here are the description templates:
More importantly, here's a suggestion for finding further examples of real descriptive data in AtoM production sites. Remember, AtoM 2.5 and later includes CSV export from the clipboard, including for public users. Because of this, you can therefore go find an existing AtoM site, add a fonds or collection to the clipboard and then export it - and compare that with how the description appears in AtoM's public interface.
We keep an example list of public AtoM sites we know about on our wiki here:
Instructions for using the clipboard, and exporting a CSV from the clipboard, for reference:
As an example, I went to the Dalhousie University AtoM site, and found a fonds there - the A.M. Smith & Company Fonds:
I've attached the clipboard export of this fonds for you to peruse. Keep in mind that Dalhousie is using the the Canadian RAD standard, so if you exported from a site using ISAD or another template, you may get slightly less columns on export.
Hope this helps!