What triggers this issue?
This issue reports all URLs that contain a double slash (after the domain part).
Why is it important?
Most servers are already set up to ignore multiple slashes in the URL path. However, these URLs may be confusing for search engines. They will be interpreted as stand-alone URLs. This can result in duplicate content issues when one page can be found at multiple URLs.
How to fix it?
First off, you have to learn where did Site Audit crawler find these URLs. To do that, add the "No. of inlinks" column to the table in this report via the "Manage columns" button.
Now that you click on a number in that new column, you will see a list of URLs that link to the affected URL.
You should then edit the links on these pages and remove the unnecessary slash.
If the double slash in the page's permalink is generated by your CMS, you might need to address your developer for help.
If the URL with a double slash is indexed in Google or has incoming external links, you can set the proper 301 redirects to the corrected URL.