If you are using a Basic (free) FullContact account, the History tab will show up to 7 days of contact history. However, if you upgrade to Premium, the History tab will show complete history for the last 6 months.
Activities are sorted and grouped by the day, and multiple similar actions (updates, edits, deletions) are grouped together.
You can access the History tab for your account from the left menu in FullContact for Web. Otherwise, if you have the FullContact for iOS app installed, you can view the History tab from the app's menu.