Oldest data point in "last 5 minutes" graph shows unreasonable values

[fastcat]

General information

1. Android Version: Nougat, Oreo (seen on both)
2. Android Vendor: Google
3. Device: Pixel C, Nexus 6P (seen on both)
4. Version of the app: 0.6.73 (play store)

Description of the issue

The oldest data point on the "last 5 minutes" graph seems to get some unreasonable / non-sensical values in it. It looks as if it is accumulating a window of up to 30 or 60 seconds of data that otherwise would have "fallen off the end" of the graph, and is then periodically reset.

So, if I have a 5mbit data stream coming down the VPN, the oldest point starts at the reasonable value, but then ticks ever upwards every second, often exceeding 120mbit/s, until it hits some limit and then is truncated back down to a realistic value.