From Meraki's documentation found here ...
https://documentation.meraki.com/MX/Monitoring_and_Reporting/Device_Utilization
MX Device Utilization Calculation
The device utilization data reported to the Meraki dashboard is based on a load average measured over a period of one minute. The load value is returned in numeric values ranging from 1 through 100. A lower value indicates a lower load, and a higher value indicates a more intense workload. Currently, the device utilization value is calculated based upon the CPU utilization of the MX as well as its traffic load.
Due to load averaging, it’s possible for transient load spikes to occur without being visible in the utilization metric. For example, a device load that is consistently shown as less than 85% may still be experiencing transient load spikes. These transient load spikes may cause packets received in excess of the device’s forwarding capacity to be dropped.