What exactly does the email at the end of the source code mean?

The captain in the source code enters Mr. Sean's body, and after 8 minutes, the power is cut off, and the captain's life in this world ends. But what everyone didn't expect was that the world in the source code didn't end but continued to run. Goodwin who received the text message is Goodwin in the code, not Goodwin who will be arrested in the first world or the so-called real world. There is also a captain in this source code world (which can be considered as a fact, parallel to the real world), but at this time the train explosion was stopped by Sean (captain), so the captain did not perform the task. The short message means to ask Goodwin to help the captain who may perform the task one day.

In fact, this film is about the viewpoint of parallel world of quantum physics, which is a novel and mysterious idea.