Congrats on Your Purchase! What you see when TV is turned on is, INFO of Time and, the 720x480 is the *Resolution* of what is being displayed. Your purchased set IS capable of displaying a "native" Resolution of, 1920x1080p. So no need to panic. I won't get too involved in what Resolutions are, just to keep as simple as possible for you..but keep in mind the LAST set of"x480" whats most important! I'll assume your set IS connected to a Cable or Satellite Converter Box via HDMI or COMPONENT Cables.
The ONLY time you will see FULL dispay of 1080p is when watching HD, and/or, Blu-Ray DVDS, via HDMI/Component cables. Broadcast Analog, Digital and High-Definition television channels..via your Cable or Satellite Providers..are displayed as x480p, x720p and/or x1080i. Did you notice the letter "i" after 1080..and NOT the letter "p"? "i" = Interlace and "p" = Progressive. Again..remember that only HD/Blu-Ray DVDs are displayed in 1080p.
I will again assume, that when you turned on your set, your Cable/Sat Converter was tuned onto a, *Analog or Digital Broadcast Channel*. These Channels are broadcast in 720x480p.
If you subscribe to/for *High Definition Broadcast Channels*, you should have a High Definition Converter Box. Your Cable or Satellite technician, if knowledgeable and courteous, should have asked you when installing your service, what Resolution you preferred when viewing High Definition broadcasts/channels. Here your ONLY choices would either be in, 1280 x 720p..or..1920 x 1080i. This decision is dependent of your viewing choices. I enjoy FAST MOVING/ACTION PACKED broadcasts such as, Hockey/Football/Boxing/Martial-Arts and I prefer the 'smoother' picture/Resolution that 720p offers, other than the "jagged" picture/Resolution, I and others see watching such broadcasts with 1080i. Again..this is the viewers choice, so I recommend you watch YOUR favorite Hi-Def broadcasts in both resolutions of 720p and 1080i, and decide which is best for your viewing pleasure.
In regards to 480i, 480p, 720p, 1080i and 1080p *RESOLUTIONS*..go to CNETS 'Tips & Tricks' and in the Search Box, type..HDTV: Know your high-res options
Thats a good starting point in explaining more in-depth about *Resolutions*. Hope this helped..not confused you understanding what the 720 x 480 means?