Custom Bandwidth: Crops the exceeding bandwidth utilization in the graph

Hi Team,

Please advise.

I have this NPM 10.7 version and and I've encountered an issue with graphing GigEthernet interfaces. Originally, the bandwidth was set to 4Mbps, if I set the bandwidth manually by checking the custom bandwidth and set it to 1Mbps on a GigEthernet port it will stop graphing anything above1Mbps. The reason why I change the bandwidth to 1Mbps is to test if it will display the bandwidth exceeding its limit in the graph but unfortunately it crops the exceeding bandwidth utilization in the graph.    Please see the attachment below.

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My concern is why it crops the data when it reaches the set bandwidth?