Ive just got a new hardtail, top loading bridge. Its brand new and all 6 saddles are set to the same height.

To what measurements should I adjust the saddles' height and length?
The string saddle's height is adjusted to match the fretboard radius and is used to set the string height above the fret for action. I use a fretboard radius guage for this and to set the poles on humbuckers to the same arc.
The string length adjustment is for setting the string's intonation. This length depends on setup and string gage,etc. Good luck.