Histogram 2.1.1 problem

I wanna make histograms with the field "Cumulative variation" as the x-axis (Values). The first histogram shows the count of items thar are in each bin. That's ok! However, in the second histogram I need to show the sum of weigts of items in each bin. In frequency I put the field Weights as sum , but is showing a number that I don't know where it comes from, it's not a count because there are decimal numbers. I tried to create a measure Sum(Weight), but the same result. What's going on?

I need to show these 1..74 in the histogram