How to calculate proper Quantum with HTB

Hello,

I am limiting egress traffic to 30Mbps (30mbit) using hbt with a leaf
class for port 22.

tc class add dev eth0 parent 20: classid 20:20 htb rate 30mbit ceil
32mbit prio 1

This all works as expected but I do see some messages in the log
during heavy traffic pasted below.

"HTB: quantum of class 100020 is big. Consider r2q change."

From what I have read the quantum is calculated as (rate in bytes per
sec / r2q-default 10).
In my case 30mbit (30000000/8) / 10 = 375000 (3mbit). The reported
quantum is significantly less but still receive the error in the
kernel log.
I read that the quantum is only used when >limit and <ceil. I am most
definitely at ceiling at all times as I pass heavy traffic.

So questions.
Is there a right way to calculate the correct quantum?
Are the kernel messages I am seeing indicative of a problem that I
should be concened with?

Thanks