High CPU usage when idle, but figures are wrong?

[Bananas-Are-Yellow]

When I first start Stacer, the Processes page shows that Stacer is using over 90% of CPU. This slowly declines over a minute to around 17% and continues to decline slowly, about 0.1% every 3-4 seconds. It's been running for about 3 minutes right now, and it shows 13.2% CPU.

Pop!_OS 20.10.
Stacer v1.1.0

However, if I watch the System Monitor, it shows that Stacer initially uses around 14% of CPU when it starts up, declining to 1% or 0% of CPU within 10 seconds.