"m"bps on the graph represents a millibit, which is a very small amount of data. The reason we get these millibits is because we are graphing bps ( Bits Per Second ), we have to divide the data we get from the router by the poll interval. So for example, if we poll every 5 minutes ( 300 seconds ), and we get 8 bytes have moved over an interface in 5 minutes, we have to convert to bits then divide by 300 seconds. So 8 * 8 / 300 = 0.21
0.21 is less than 1 bit per second, so we plot it as 0.21 mbps which is 0.21 milli bits per seconds.