The MessagesInPerSec metric reported by the Kafka agent monitor is reporting wrong value.
In the jmx.yaml located at extensions/KafkaExtension/config/modules/kafka/jmx.yaml, the metric type "Rate". It looks like the agent is aggregating over 15s intervals and reporting the value.
snippet from the jmx.yaml for the metric.
- objectName: "kafka.server:type=BrokerTopicMetrics,name=MessagesInPerSec,topic=*"
attribute: "Count"
metricName: "{rootNode}|KafkaServer|BrokerTopicMetrics|{topic}:Messages In Per Sec"
metricType: "Rate"
Use the following metric which should report the proper value that you expect.
SuperDomain|<Hostname>|kafka-monitor|kafka-operator|Kafka|Brokers|kafka-broker1_9393|Default|kafka.server|name=MessagesInPerSec|topic=<topicname>|type=BrokerTopicMetrics:OneMinuteRate