That is just a text file - but the data is a base64 encoded serialized array of all of your redirects. I did not have time when I was programming the release of the plugin to finish that section and make it easier to read, so that was the best solution at the time.
I do have a page set up where you can convert the file contents into a readable set of redirects (one per line, PIPE separated). You can use it as much as you want until we have the new version of the plugin out which will solve that issue.
You can find it here:
Just copy the content into the textarea and click process. It will give you a clean file to edit. Then if you want to restore them on your site, paste the edited file back onto the textarea on the same page and click process again and it will output the data in the correct way to restore them on your site (it detects if it is encoded or readable automatically).
Hope this helps a bit.