It is a small mistake on page 8 ( ..-debpackage/... -> ..-deb-package/... ):

Wrong:
bash <(curl -sL https://raw.githubusercontent.com/node-red/raspbian-debpackage/
master/resources/update-nodejs-and-nodered)

Right:
bash <(curl -sL https://raw.githubusercontent.com/node-red/raspbian-deb-package/master/resources/update-nodejs-and-nodered)

Best regards,
SFL