String Action Question

[JosephEMG]

Hey guys, I set up my guitar yesterday and got the action as low as possible without buzzing and a good tone. But I got two readings, I got it at the 12th fret and at the 17th fret. Which one is the correct one, or is it relative?

I got these numbers:

High E
1.8mm at 12th
2.0mm at 17th

Low E
2.1mm at 12th
2.3mm at 17th

 

[AwDeOh]

It's usually measured at the 12th. You need that graduating height (as you can see at the 17th) to prevent string buzz.