How to interpret a two-sided graph? 
What does the "right" Y-axis represent?
Taken from here: https://istheservicedown.co.uk/status/virgin-media/2654675-bristol-bristol-england-united-kingdom

Looking around the provided site it looks like the blue curve represents the number of reports for Virgin Media outages in the UK, whereas the green curve is the number of reports specific to Bristol.  The units on the left are for the blue (country-wide) curve, and the units on the right are for the green (local) curve.  For example, consider the excerpted images below.  Note that in each case the blue curve matches the graph of total Virgin Media outages, whereas the green curve (and corresponding scale on the right axis) change depending on locality.
Virgin Media outages in the UK:

Virgin Media outages in the Bristol:

Virgin Media outages in the London:

