How to use ssh admin interface commad - 'get bandwidth wan x y'

The ssh admin interface has the command 'get bandwidth wan with this description:

> get bandwidth wan
Unsigned integer Connection ID
Unsigned integer Measurement period

What does the measurement period parameter do?

I assume this command

> get bandwidth wan 1 120

will show the bandwidth summary for wan 1 over a certain period – does it show the average over the last 120 seconds?

I don’t think that parameter is valid for this command because it is a real-time snapshot of the WAN connection(s) current throughput by protocol.

Ah – so the summary is just wrong?

If you type this:
> get bandwidth wan 1 ?

you’ll see this summary of additional parameters …
Unsigned integer Measurement period