problem encountered running 'npm start' in "Programming WebRTC" book

Hello Karl @karlstolley,
In the section called “Finding Your Way Around the Code Directory” you write:
“…you can simply run npm start on your command line to fire up the server”.

But doing so I get:

ksrtc@0.2.0 start

PUBLIC=www DEBUG=signaling-server: node ./scripts/start-server

‘PUBLIC’ is not recognized as an internal or external command,
operable program or batch file.

Can you please help me with this.

Yehuda