Line around Smith chart when measuring using VNA

When Im measuring by VNA , I always see line running aroud
the smith chart side.
what does it mean ?
good or not ?

thanks

would you mind clearing out your question so that people here may help you ?
whats a VNA ?
what do you mean by " a line running around the smith chart side"

This is a sign of long transmission lines. Did you calibrate your VNA with the cables used to hook it up to the circuit being tested?