Thanks Lustyd. Now you’ve said about them needing to stay put it seems obvious. How bizarre that Scott bother writing any numbers at all if they are not correct. I will adhere to your advice – I shall just halve all of the torque numbers to ensure they’re consistently tight across the bike. On my Spark they state 10 Nm except the main frame pivot which is 20 Nm. The top shock bolt is stainless and requires 10 Nm but reverse thread (which my wrench doesn’t measure) so I have always just done that up as tight as feels right.
I have been kicking myself about this bolt-rounding incident because I am normally careful – a real manual-reader.

Once my LBS ‘checked’ my pivots as part of a service and the bike was creaking like crazy so I backed them all off and re-torqued myself… and then they were okay.

Thanks everyone.
It’s the hollow main pivot bolt that is marked 83.5 MM.
I have used the correct tools, my torque wrench is nothing special but it usually works okay. I guess I loosened & tightened the bolt too many times – the aluminium seemed a bit lightly built for such a big pivot + 20 Nm.