the network Data received/sent figures in Yosemite 10.10.5 Acticity Monitor Network pane are wrong. For example, sending data at 35-41MB/s results in a bottom right figure of about 200MB/s - 265MB/s. If you're trying to show Mbit/s, that's a lower case m, and you're calculating it wrong.
Mac Pro, OS X Yosemite (10.10.5), 10Gbit Dual port ATTO Fiber Card