substream
How many sub-streams the member consumed against the block it was given, once it has been released; null when the factory does not track it or the member has not been released.
A member that consumes more than its block runs on streams belonging to the next member's block, so the two are no longer independent and a concurrent study is no longer reproducible cell by cell. Recording it lets a finished study say which cells that happened to.
Parameters
member
the member's index