Hi @sash19, welcome to Dask community!
I didn’t find the source code, but I think this comes from psutil, monitoring the worker process CPU usage on the system. Since your process has several threads, it can potentially use up to 800% CPUs, meaning 8 full cores (or virtual cores). So I don’t think this is a bug, it is just system metrics.
However, the Total cpu usage is wrong, it should either be the sum of all usages, either we should reduce it to a percent of thread level usage.
cc @crusaderky.