Activity Monitor, Excel, and packets sent and received

I have Activity Monitor configured to show packets sent and received. Earlier today, Activity Monitor said Excel had sent something like 40 packets and received something in the 80s. Now Activity Monitor says Excel has sent 28 packets and received 41. I neither quit Excel nor restarted the Macintosh. How can the number of packets sent and received go down? Is this an Activity Monitor issue, an Excel issue, or something else?

Thanks for any education, and feel free to bash Microsoft for having Excel send and receive packets at all. I sometimes operate with no internet access, and Excel will sometimes be unresponsive for a full minute while I assume it is trying to contact the mother ship.