Hey Mal,

There are honestly quite a few different things that could be playing a factor in the differences you're seeing between PingPlotter and a command prompt ping. We've actually got a knowledge base article that goes over some of the possibilities here (as well as some potential solutions), which you can find here:

http://www.pingman.com/kb/37

Hopefully this helps out! If you have any questions - please let us know.

Best wishes,

-Gary