FR+NM stands for "FullRecord + NeatMessage". You will see this window:
At the global level, you may specify a rule to override the auditing of the message. If you issue a message which have only one button with this particular text ("Message"), this message will not be audited in the audit file.
For example
Message('This message will not be audited','Warning',ICON:EXCLAMATION,'Message')
The "Message" button will be shown as specified below, in this case "Ok". The result of this call you can see it below:
If you think that the proposed text ("Message") might be confused with another that you often use, then just replace it with something more exotic (like "jfrw94") so you will be sure that you never use this signal without meaning it. The button will show to the user as above, anyway.