Pardon my ignorance but how does one measure that?

 

With a torque wrench, such as:

 

http://www.halfords.com/motoring/garage-equipment/hand-tools/halfords-professional-torque-wrench-60-300nm

 

I'm sure there are cheaper/better, but a quick google brought that one up.

 

(but not that one, 'cos you need one that measures lower than 60nm!)

Thanks matey. I'm quite surprised they expect customers to know this.

 

I just did it up as tight as I could by hand and tugged on the bar to check its secured.