create Value range summary

[linhnguyen]

Hello,

I am trying to create a value range as the chart at the bottom. I look at the current chart and extension collection, but it seems that there is nothing available.  Can anybody let me know if I can create the bottom chart? I created a box plot, but its indicators (median, mean) are not identical. 

the measure used in this chart is the time taken to complete a task. Minutes=(endeddate)-(starteddate)

Box plot and distribution charts: 

dimension: Minutes

Measure: Avg(Minutes)

mean is 614 (not correct)

can anybody help me with this?

thank you