These can often be different versions of the "same" URL, which Wayback subsequently groups together. If you mouse over each one, you'll notice slight variations in the URL. For example, there may be an http and https version or a www and non www version of the site.
You may also notice multiple captures from the same date.
This happens when Umbra detects component URLs initially missed by Heritrix and prompts Heritrix to re-crawl the URL. In these cases, there will be an asterisk beside the dates on the calendar page where new and/or changed data was captured. You will also notice the time stamp in the Wayback link differs for each calendar entry:
Visit "Archive-It Crawling Technology" for more information about how our crawling technology works.
If you are concerned that these seemingly duplicate entries were made in error, please contact our Web Archivists directly for assistance.