A key point of the plot is that the mailing labels are given nonexistent addresses so that they will be lost in the 'dead letter office.' USPS-linked addressing software does not permit labels to be generated unless the delivery address is validated in the database.
When Seeley picks up the tickets from the world series you can clearly see their seat numbers; 3 and 4.
But when he looks over at the chairs he brought home in an earlier episode the camera focuses seat number 2 and 3 and fades out 1 and 4.
IF those even are the seats from the correct row.
During the animation of the murder, Angela says that the subclavian artery was nicked. On the images however, it is probably the carotid artery being cut, since the subclavian is much lower, passing underneath the collarbone.