Kubernetes: understanding memory usage for "kubectl top node"

How do I interpret the memory usage returned by "kubectl top node". E.g. if it returns:

    NAME                   CPU(cores)   CPU%      MEMORY(bytes)   MEMORY%
    ip-XXX.ec2.internal    222m         11%       3237Mi          41%
    ip-YYY.ec2.internal    91m          9%        2217Mi          60%

By comparison, if I look in the Kubernetes dashboard for the same node, I get: Memory Requests: 410M / 7.799 Gi

How do I reconcile the difference?