since our step granularity is 5 min, in the first 5 min, the start and end of alerts will be the same, since the datapoint is only 1. This generates an invisible bar for the first 5 min. 

From Ivan: we have step=5m, it might make more sense to add the 5 minutes prior: as we can't tell when exactly it happened: so it's equally probable it started now or 5 minutes ago, but with the latter, we have nicer bar to show