Need to adjust my c0 readings at my brothers work (mot station) as it has been tampered with

what should my c0 readings be ? Can't find anything on auto data or google for stock settings

 

You want to check everything else as well (pressure/timing/ignition timing etc) is all where you want it to be FIRST as its pointless setting CO on a non-setup engine. Then aim for 2% @ idle as a real benchmark, if you can get it lower and its happy then great.
Its not really as simple as "set it to xx%" tho