You can find the a "total sales" value n in both your "Sales over time" report and your "Messages sent over time" report. However, these numbers may differ:
Sales over Time
Your "Sales Over Time" report displays all of the transactions that occurred over the timeline you've selected. The messages associated with these sales would have been sent before the sale took place and may have a send date outside your selected timeframe.
Messages over Time
Your "Messages Over Time" report displays all the messages you have sent over the timeline you've selected. The resulting sales are based on those messages' conversion values, regardless of if the purchase was made outside the selected timeframe.