I found another cause for this error in this awesome guide for the pf filter
"""
realtime: the amount of bandwidth that is guaranteed to the queue no matter
what any other queue needs. Realtime can be set from 0% to 80% of total
connection bandwidth. Lets say you want to make sure that your web server
gets 25KB/sec of bandwidth no matter what. Setting the realtime value will give
the web server queue the bandwidth it needs even if other queues want to
share its bandwidth.
"""
See the 80% limit of the realtime value.
More on: "https://calomel.org/pf_hfsc.html"