I play guitar and can read both sheet music and tablature, and if I had to guess, this is what I think: The words are just there to, more or less, tell you when to play something, and the numbers should be what you actually play. When you see:
|--------| <- Highest string on a four string bass.
|--------|
|--------|
|--------| <- Lowest string on a four string bass.
The numbers indicate what fret you should press down on that particular string, so a 3 on the bottom line would be the lowest string and the 3rd fret. The G, D, A, E near the bottom is odd, because normall it would be at the very beginning (in my experience), because that is probably the tune of the bass, meaning: The lowest string should be the E note open (when you are not holding down any frets), the second lowest string should be A open, etc. That is standard tuning, though, so it shouldn't require much change for you.
I hope that helped you out a bit. You may want to try this song or pick another familiar song and try playing what you think it means. If it sounds like the song you are doing it right.

If you still do not understand please feel free to post and I will try to do a better job of explaining.