How does release burndown chart work for a few scrum teams working on the same release?

[Marek Skowron]

Hi
I would like to use functionality release burndown chart.
I wonder if and how this functionality works for many scrum teams working on the same release.
We used custom field for planning releases - but recently to use power of JIRA we switched from custom field to Fix version field . As the result of action we received chart from enclosed picture. As you can see there are 5 scrum teams which in parallel work on release 1.0.0.
Does release burndown chart work for many scrum teams working on the same release?
Why wasn't  work added added to all teams in sprint 7 (tickets were added to release and not to sprint backlog of team 5)? I would expect that post for each team looks the same for each sprint.
Why does velocity per sprint is 12? Shouldn't it be at least 42 = (36+66+26)/3?
Board was created as a scrum board based on the filter: fixVersion = "1.0.0"

[Marek Skowron]

I figured out why JIRA calculated velocity of the team per sprint to 12SP.
It calculates it not using 3 sprints for the all teams but each bar/post is treated as a sprint.
Velocity per sprint = 36SP/3 sprints=12SP 
So it looks that this feature doesn't work for my case.
I have to find way how to force JIRA to do what I want.  Assigning tasks to one virtual sprint aggregating all sprints (?) - additional effort :(