what does it mean when the milage goes off and the word "DECK" comes in its place?

Hello, this would appear to indicate an error occurring within the read out display or related components. Reviewing the workshop manual in brief, I do not see anything indicating the word "DECK" appearing, so I can't really suggest much more than a hands on evaluation. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops

IT MEANS TRUNK IS OPEN... IT SHOULD SAY REAR then DECK MEANING YOUR TRUNK IS OPEN