SES Dashboard Send count vs Bounce count

Firstly, the second graph you've captured pertains to the bounce rate metrics rather than the count of bounce events.

Regarding bounce events, there are two distinct types: asynchronous bounces and synchronous bounces. A synchronous bounce occurs during active communication between the email servers of the sender and receiver. According to the details that you have shared, it looks like there hasn't been any recorded instance of a synchronous bounce as previously mentioned.

On the other hand, an asynchronous bounce happens when a receiver initially accepts an email message for delivery but subsequently fails to deliver it to the intended recipient. It's important to note that asynchronous bounces can occur at any time, and recipients might send back bounce notifications even during weekends for emails sent to them during weekdays.