RetryAttempts access log field is not populated

I have a retry middleware set up and attached to the web port. In the debug logs, I can see that the retries are being carried out when required. However, the RetryAttempts field in the access logs is always 0, no matter how many times the request was retired before it succeeded (or failed).

Am I correct in thinking that this is what the RetryAttempts field is meant to show? Or am I getting lost in what it actually represents?