Why this discrepancy and any suggestions on how to avoid it?

2017-12-21 00:00:00 ZSAN VXLELNXHWMSL: $0.67   ZSAN VXLELNXHWMSL                                           close    high     low    open  volume
symbol            time                                                       
ZSAN VXLELNXHWMSL 2017-12-20 15:56:00  12.800  12.820  12.800  12.820   700.0
                  2017-12-20 15:57:00  12.800  12.820  12.800  12.820   700.0
                  2017-12-20 15:58:00  12.800  12.820  12.800  12.820   700.0
                  2017-12-20 15:59:00  12.934  12.934  12.934  12.934    64.0
                  2017-12-20 16:00:00  12.800  12.800  12.800  12.800    15.0

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