I thought the definition in the rules was quite clear, but it clearly is not so . Thank you very much for asking this question!
If your robot started in the penalty area in front of the blue goal, your robot should face the blue goal. The line in the rules which would be responsible for this currently says
the robot starts from its own penalty area oriented towards the goal.
whereas it should say
the robot starts from its own penalty area oriented towards the closest goal.
Provided your robot started facing the blue goal, the left corner of the field would be the left corner of the actual space on which the game can be played (i.e. the corner where the two white lines meet).
In order for the challenge to be actually challenging, if your robot started facing the blue ball, it needs to score on the yellow goal.
Thanks a ton for the question again -- it shows that a lot can be done with regards to clarity improvements of this section of the rules.
If you had any other questions, please do not hesitate to ask them here.