Steady-state error (SSE) is proportional to the process gain and inversely proportional to proportional gain.
First of all I'm not able to understand what "process gain" actually means and how it differs from proportional gain. Secondly, I can't understand the relation between SSE and the two gains.
PS. I haven't taken a formal course on Control Systems and I'm just a hobbyist trying to make a PID controlled line follower at home. So, it might be the case that I've totally missed something important.