The collection merely shows what cars you have acquired at least one example of during your time playing. It isn't a reflection of what cars you currently own. If you want to 'access' the other 86 cars, you'll have to purchase them again.
This would be the other way round, garage would have more than collection.
Collection is counting each individual unique car ever in possesion.
Garage is counting each individual car currently in possesion.
If Collection > Garage, then you have sold cars.
If Garage > Collection, then you have multiple individual identical cars.