If you open the airport customization page, it will tell you which one is in use right now.
You have multiple files, because you customized different versions of the same airport.
Even if it was the "same" airport, if the scenery was updated, and your profile contained parking mismatches, GSX would have warned you about this, suggesting to either create a new file containing only matching parking spots, or an entirely new file. So you have multiple files for the same airport, depending what you replied to those warnings.