My bike got it's first service at the dealer and they also tensioned the chain.
I'm struggling to understand how the tension is measured. It should be 2-5 mm from the top of the chain to the flat part (and not the ridge) below the bridge, right?
When my bike had it´s first service they over tightened the chain, I was on the motorway on the way home when I noticed the excess noise. (Not going to use them again, and it was a three hour round trip ) As @Tom shows in the video is the correct way I do it. I clean and lube the chain first though.