Hi, @rtblovers. Thanks for your question and sorry for the delay in getting back to you.
This difference could be due to the date range specified. When passing in dates without times, the end date is exclusive. This means that setting end_time=2016_09_08 will include data through 2016-09-07, but not data for the 8th. If you use granularity=DAY, you’ll notice that the billed_charge_local_micro array only contains six elements with the specified date range. The UI includes data for the seventh day.
Please let us know if this clears things up.