The Usage sent and received numbers relate to the selected time interval next to the graph at the bottom of the page. These numbers are updated periodically with the cloud controller and are compounded between disconnects and reconnects.
Note: Depending on the selected time interval, the Client Usage can take around 20 minutes to be compounded and displayed on Dashboard.
I suggest you open a support case.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
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