How does Jira Portfolio calculate duration, minimum work package size doesn't seems to be considered

[Nicolas Gendron]

A ridiculously small items in my portfolio (180 story points) takes, in length, about half of an items with 2160 story points.

I only have 1 team defined and no releases exist as of now.

I tried to play with the "Minimum Work Package Size" parameter and put it at 60 (so, 3 sprints to do the small items) and nothing seems to change, even recalculating does nothing.

Any ideas? 

[Nicolas Gendron]

I still don't understand why, but it seems that when a high level item in the portfolio has child issues and the other not, this has an influence.