Clickshare IDs are generated and added to each link in the email, and are used to track clicks.
However, if a user clicks on multiple links within the same email, they will be assigned multiple Clickshare IDs, even though they are the same user.
If a user visits your website multiple times, they will be counted as multiple unique visitors. This can happen if a user clicks on multiple links in the same email, or if they visit the website multiple times in a day.
So it is possible that becaise of any of these reasons you are seeing the mismatch