Howzit,
You can go to www.passmark.com and download "DiskCheckup" for free. Here it will give you the values as well as the threshold. For instance my Western Digital has a Read Raw Error Rate value of 200, worst is 198, and the threshold is 51. As yours is a Seagate, I don't know whether each manfacturer has different value sets. It wouldn't make sense if they did. That being said, your values are way low and I would say that it would be safe to go ahead and do a total backup and purchase yourself a new HDD. Find the lowest price with the greatest capacity for your budget here: www.pricewatch.com This should be the first website you ever go to when on the prowl for new components. I hope this all helps!
Respectfully, SixDOF