Can someone help me understand why, in the last two interactive figures, the "Difference of Summed Areas" signal leads the "Actual Satellite X Source Data" sign

Can someone help me understand why, in the last two interactive figures, the "Difference of Summed Areas" signal leads the "Actual Satellite X Source Data" signal? It seems as though the receiver signal is almost predicting the source data bit changes, which should not be the case.