Very few spare sectors are left of your HDD,run seatools SMART test to see if their are any errors and if their are no errors then your HDD is fine.....remember one thing Seagate will replace your HDD if it fails SMART test through seatools.....For your satisfaction you can run Error scan in HD Tune also....
Rellocated sector count is spare sectors in your HDD which helps HDD to transfer your data to spare sector if any sector is getting damaged.....HD shows this warning when very few spare sectors are left..... Run seatools and HD Tune error scan to see if it shows any bad sectors