There are graphing programs available outside of MikroTik which can graph at 1 minute intervals, although its resource intensive with a large number of hosts & thus usually avoided.
The graphs are not 100% accurate because they're averages of data over a 5 min polling period, but they give a fairly good idea of how much data is going across the line. The more often you poll, the more accurate the graph will be, and the higher rate it'll show.
IT consultant. Network manager. Packet junkie.