Scatterplot graph y-axis displaying times

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In the second assignment I have created Date objects, setthing minutes and seconds to be the same as for each Time field, before adding each of these Date objects as a new property to each of the objects contained in the json file:

  var date = new Date('01-01-01');
  date.setMinutes(mins);
  date.setSeconds(secs);
 json[x].TimeInDateFormat = date;

The yAxis is displaying numbers going from 09,420,000 to 09,580,000.

I would like to display these times in the required format of ‘mm:ss’ but don’t know how to do this, or where in the code to make changes.

Could anyone advise me on how to proceed?

Thanks for reading.