Sorry, Naomi, I haven't been on here for a couple of weeks, so didn't see your post.
In2 is a notification that Supplementary work is due on the car. These are serrvice items in addition to the 12 month/10,000 mile and the 24 month/20,000 mile services, falling due at longer intervals than these Services. Details are in the car's Maintenance Record booklet, and can also be found in the Haynes Manual for the A4, although this does not cover the 2.6 engine. You can also find details of the services and intervals online.
Other notifications are OEL - Intermediate Service, mainly oil and filter change - every 10,000 miles, and In1 - Maintenance Service - every 20,000 miles.
The mileages may be different for your car, those quoted are for 1996 A4 (B5) 1.8 Turbo.