Yes, the exchange supported spread reverts back to zero for the next day's open, and it is quoted in terms of net change for the day.
Exchange Supported NoB Daily:
Exchange Supported NoB 60 minute interval:
A synthetic NoB expression better showing the longer term trend:
Yes, the synthetic expression would be required to chart it properly longer term. Which is always a very good idea. This shows why simply fading moves intraday is not always an act of brilliance.