I work off two sources of info for build data.
There were 534 E91 D3 BiTurbos produced across the globe as per the Alpina-Archive.com and your car is the 89th built
Then if you want to know the number of cars built to UK spec the Alpina Register UK Production Stats table shows there were 85 built.
I believe the UK Production numbers, split by year, is based on the dates Sytner delivered them as new cars.
You then have the Register and Archives which aim to display photos of each individual vehicle built. The difference is that the Register shows vehicle images/descriptions where a current or previous owner has submitted details (can be global) and for the UK built vehicles, all are listed based on data Sytner provided and shown as Alpina GB-owned where no other info is available. The Archive however, is based on the build data provided by Buchloe and is populated by either: owner submitted data or by the team who review for sale ads and add this info to the Archive. Because each vehicle of a particular model is sequentially numbered, it is safe to assume that where a vehicle does not appear on the Archive, it's never been spotted in the wild to date. As in the case of your car, if you would like to add it to the Archive, I can organise that.
Hope that helps.