Bandwidth graph is anomalous around 5 minutes ago

As my realtime bandwidth graph progresses, about 4.8 to 5 minutes ago is always 2-10 times higher than the rest of the graph. It moves around a bit, but it always looks something like this:

This is with client 2.5 on my Mac running 10.10.2. Is this somethingI can fix, or a bug in the client?