[Observium] Need Explain about Legend Details on DiskIO Graph

Dear All,

Can someone explain me the details of legend on Disk IO page refers to ? Health > Disk I/O:

First graph with legend bps "<" & ">" (blue and green graph) What does k, M, none suffix mean ?

Second graph with legend Operations/sec "Rx" & "Tx" (red & orange graph) What does m, u, none suffix mean ?