There are two different report types you can choose between when connecting the Mailchimp data source, Default and List Growth History. The latter will give you a summary of the month-by-month growth activity for all the lists.
The data you can get from the List Growth History report :
Dimensions
Month
List ID
List Name
Metrics
Subscribed
Total subscribed members on the list at the end of the month.
Unsubscribed
Newly unsubscribed members on the list for a specific month
Import
Opt-ins
Newly opted-in members on the list for a specific month
Reconfirm
Newly reconfirmed members on the list for a specific month
Cleaned
Newly cleaned (hard-bounced) members on the list for a specific month
Pending
Pending members on the list for a specific month
Deleted
Newly deleted members on the list for a specific month
The data you can get from the Default report :
Dimensions
Campaign ID
Campaign Name
Campaign Type
Click-tale Tracking
From Name
GA Tracking
List ID
List Name
Send time
Subject Line
Variate Child ID
Variate Child Name
Web ID
Metrics
Abuse Reports
Total number of abuse reports generated
Click Rate (total)
The total number of clicks divided by the total number of successful deliveries
Clicks
Total number of Mailchimp clicks
Clicks Unique
The total number of unique clicks for links across a campaign
Delivery Status
Emails Sent
Total number of emails send
Emails Canceled
Total number of emails canceled
Facebook Likes
Total number of Facebook likes
Facebook Unique Likes
Total number of unique Facebook likes
Forward Opens
How many times the forwarded campaign has been opened
Hard Bounces
Total number of hard bounced email addresses
Open Rate (total)
The total number of opens divided by the total number of successful deliveries
Opens Unique
The total number of unique opens
Recipient Likes
Number of recipients who liked the campaign on Facebook
Soft Bounces
Total number of soft bounced email addresses
Subscriber Clicks Unique
The total number of unique subscriber clicks for links across a campaign
Syntax Errors
Total number of addresses that were syntax-related bounces
Total Forwards
How many times the campaign has been forwarded
Total Opens
Total number of opens
Total Orders
The total orders for a campaign
Total Revenue
The total revenue for a campaign. Calculated as the sum of all order totals minus shipping and tax totals
Total Spent
The total spent for a campaign. Calculated as the sum of all order totals with no deductions
Unsubscribes
Total number of unsubscribed members
The data you can get from the Click Performance report :
Dimensions
Campaign ID
Campaign Name
Click URL
Click URL ID
Date
Metrics
URL Clicks
URL Clicks Unique
URL Click Percentage
URL Unique Click Percentage
Note that the Default report contains similar Click metrics. These metrics are grouped by Campaign and will therefore have different Unique values than this report, which is grouped by Click URL ID.
Also, please note that the Date dimension in the Click Performance report is the Campaign Send Date. It is not possible to attribute this report on Click Date.