I was about to write something similar, but Thom A beat me to it. In my case, both precedent constraints are "Logical OR, one constraint must evaluate to true" so both constraints coming from the Initial task (C170... here) would be dashed green lines, with mutually exclusive conditions.
E.g., at the end of a control flow, the decision to run a file archive step depends on if the package is running in production. If it is in production, run the archive step, if not, branch around it.
The precedence expressions for the branches out of C170 are:
@[User::_SQLDATABASE] != @[User::_PROD_DB_NAME]
@[User::_SQLDATABASE] == @[User::_PROD_DB_NAME]
In your case, you'd probably want to use the value returned by the script task in the contraints to control branching.