Strange readings from BQM

I monitor my parents' ADSL connection using the BQM

They rarely use their connection, only reading emails, and very light surfing, about 250-500 MB per month.

Over the last week, I've noticed what looks like activity every day.

Here's an example

http://www.thinkbroadband.com/ping/share/731bb430f0a...

They were actually on holiday that day, I've checked the router logs for DOS etc, but nothing, so what's going on ?

It's a small rural exchange, so is it congestion causing the latency bursts ?

Nothing to be concerned about, it appears to tie in with periods of evening traffic.

Nothing strange about that at all.

It just shows a very slight increase in latency in the evening when more people are at home using the internet.