You can view the most seen messages in your bot by clicking on "Most Seen Messages" under Analytics in the left hand menu:
The most sent message stat is defined by how many times the message has been sent out. Ordered by the most to least number of times the message has been sent. It does not take into consideration the number of users, simply the number of clicks.
Please note - statistics for messages that have since been deleted are hidden by default. You can unhide these messages by clicking "Show deleted messages":