How tight is 3nm

Burtspieeater
Burtspieeater Forum Participant Posts: 114
edited March 2014 in Parts & Accessories #1

Good morning Folks 

For once a thread not discussing, dogs/late arrivals/Club Rules etc 

I am about to fix my Thule Roof bars for the first time. The instructions say tighten the allen key (T shaped with a 50mm handle) to 3 NM. How tight is this, fairly/very?