Question on "bars in test" backtesting on M15

 
Suddenly I was caught by this puzzling behavior of MT4, say  Use Date: from 2017.06.13 to 2017.06.14, supposed to be the span of 1 day. On M15 timeframe, it should be (of 1 day) = 4bars/hour x 24 hours = 96 bars. Yet the backtest report says "bars in test" is 1097 bars! Can anyone explain this peculiar behavior?
 
Wilson Wong: Suddenly I was caught by this puzzling behavior of MT4, say  Use Date: from 2017.06.13 to 2017.06.14, supposed to be the span of 1 day. On M15 timeframe, it should be (of 1 day) = 4bars/hour x 24 hours = 96 bars. Yet the backtest report says "bars in test" is 1097 bars! Can anyone explain this peculiar behavior?
The tester always offers approximately 1000 bars of history (before test date), so that the EA being tested has data in the past to analyse when it starts.