If anyone is interested, here's an easy way to measure your TV's amount of overscan. I did this some years ago when I was learning Proshow Producer. The range is from 85% to 100% and if you load the file into Vegas, the values agree with your safe area settings. Here's a screenshot.
Simply download the file and "play" it on your TV. Here's the Dropbox link
https://www.dropbox.com/s/ykxf37o23ofdlrk/Safe%20Zone.mp4?dl=0
Just thought I'd share.
wwaag