It's honestly hard to tell from the pic... but it looks like each string has it's own individual method of raising and lowering them.

I'm just guess here, but it looks like the screwes at the back are for intonation and the two small screws over each string might be for raising each string independently using an allan key or something.

The other 4 screws are what attaches the bridge to the guitar so you don't want to touch those.


Like I said though, I'm not familiar with that bridge setup so maybe try Googling the guitar manufacturer for more info.
Usually, decent quality guitar manufacturers have ideal string height recommendations along with instructions on intonation, bridge and d truss rod adjustments.

Looks like ya have nice pickups btw. I added on a handmade one of those to the bridge pickup on my Gibson L6S and it made a world of difference to the overdrive, sustain and crunch. :)


-----------

For the one octave thing. If you finger a note exactly 12 frets higher it will be the same note just one octave higher.
So if you have your bottom E string lowered to a D. (Drop D Tuning) If you finger the 12th fret it will also be a D, but just an octave higher.
To get an E note you'd press on the 2nd or 14th frets.