The severity level of interesting responses is "Informational".
Normally response code like "200 OK" is the request has succeeded and "404 Not Found" is the server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent. The 410 (Gone) status code SHOULD be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable and has no forwarding address. This status code is commonly used when the server does not wish to reveal exactly why the request has been refused, or when no other response is applicable.
The module's intention is to log responses with codes which aren't 200 nor 404. Also, these issues are strictly logged for informational reasons , they are a heads up that the behavior of the webapp deviated from the norm in some way.