Of course you're confused, your avatar pic says it all.
But, what seems to be wrong? The video preview shows correct changes in readings and you tested them all well. And it worked well, didn't it?
So now you know what each of them say, how to reset them (in the beginning if you have to), and it can detect where the phone is tilting exactly.
Except, two problems: the Beta -179 goes to plus 180, suddenly which can cause problems if you're performing actions relative to Beta values... The sudden jump. But it can easily be resolved by some math. Search on this forum you'll find many similar problems and solutions.
Second, if you're worried about the sudden wrong readings due to spikes and jerks, you can easily eliminate that by 'easing' out the values. i.e. Instead of showing "exactly" what it the sensor reads, let it gradually go towards the value, which helps in filtering wrong values in between (i.e. jerks).
You can do that by using the 'lerp' function... Look it up.
Example: alpha_value = lerp(alpha_value, Touch.alpha, 0.4)