Bar Chart showing Created and Closed

In a Quickbase chart, which is really just a summary report in a visual format or a table report, a record can only appear once on a report, either as a record or summarized into a summary report or chart.  Hence your problem of how you can show the same record on two different bars.  

My suggestion is to make a helper table with all the 1st of the months  for the next 20 years. So a few hundred records and may be a few more if you need to go back in history.  Then you can create two Formula Query fields to total up the number of records which have open or close dates respectively during that month. 

Then create your charting off that helper table.