T/Spark wants 10W40. Semi-synthetic is fine, since it's what they put in at the factory.
That Q8 semi-synth' stuff has an API rating SL which compares to the synthetic SM (a touch "better" as you'd expect) but the car only wants SH or something.
The Operator's manual will list the grade and the API rating the oil has to have.. but as a rule of thumb, it's basically impossible to find a semi-syntheric oil that doesn't meet the minimum rating the engine needs.
12,000 mile change intervals is good.. the T/S helps it's cause by needing top ups every few thousand miles or so..
so it's getting "fresh" oil added to it all the time.
Any semi-synthetic will survive 12k in the T/S engine... but since it's cheap at that bulk price, why not change it every 6,000. That reduces the build-up of gum and varnish which 12,000 would suffer from (albeit based on my experience only around 6-digit mileages).
The Q8 is ACEA B4 though which is quite a new spec' and means extra detergents compared to B3.. What's not to like?