Underflow in Stats Channel RecursClients value?

Summary

It looks like we may have an underflow condition in the Stats Channel RecursClients value

BIND version used

Reported by a customer using 9.11.7-S1

What is the current bug behavior?

A customer who is using the statistics channel to monitor BIND behavior tells us:

Hello,

We have our DNS servers configured to collect stats. We have metrics servers collect the data so it can be displayed.

The data for the RecursClients stat randomly is a very high number. See below.

This is happening on a number of my servers.

name="RecursClients">18446744073709551440

name="RecursClients">18446744073709551426

From another server.

name="RecursClients">18446744073709551518

When I do an "rndc reconfig" the counter will clear out. But in a few seconds it will jump back up.

What is the expected correct behavior?

Obviously the customer does not actually have on the order of 2 ^ 64 recursive clients.