Fix #3612 - reverse sign in difference calculation (#3646)
Fix #3612 - reverse sign in difference calculation (#3646)


alanmcruickshank/superset-dev,apache/incubator-superset,timifasubaa/incubator-superset,mistercrunch/panoramix,timifasubaa/incubator-superset,mistercrunch/panoramix,dmigo/incubator-superset,airbnb/superset,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,alanmcruickshank/superset-dev,dmigo/incubator-superset,dmigo/incubator-superset,timifasubaa/incubator-superset,airbnb/superset,airbnb/caravel,airbnb/superset,zhouyao1994/incubator-superset,alanmcruickshank/superset-dev,mistercrunch/panoramix,apache/incubator-superset,apache/incubator-superset,dmigo/incubator-superset,mistercrunch/panoramix,alanmcruickshank/superset-dev,airbnb/caravel,apache/incubator-superset,apache/incubator-superset,zhouyao1994/incubator-superset,airbnb/caravel,airbnb/caravel,airbnb/superset,timifasubaa/incubator-superset,zhouyao1994/incubator-superset