How to remove a monitored router and historic data (5.0)

We are seeing traffic utilisation reports showing >100% usage. Bandwidth/link speeds are correct. I believe this may be because our routers are configured for "timeout active 5" and not "timeout active 1" as per your recommendation.

I want to remove a router from Netflow to reset the data, to make sure the new "timeout active 1" setting has taken effect and resolved the percentage problem.

I have tried disabling Netflow on the router, unmanaging and then deleted the router under License Administration. But when I re-enable Netflow on the router a few minutes later, it seems to come back in exactly where it left off, all the historic data (with the >100% figures) seems to be remembered!!!???

We may also come across this issue when managing the network within a 100-interface license, because we may wish to remove some routers to make room for others, etc, and then add some removed routers back into NFA later etc - when we do this we don't want old data to be remembered (or take disk space!).

I don't understand why deleting a device does not destroy everything NFA every knew about that router. Could you please advise on how I can cleanly, and completely remove a router from NFA?