Windows adds a comm port every time you add a device that uses one. So if you keep adding USB devices, (or sometimes the same USB device but plugged into a different USB port) Windows will reserve the old comm port(s) and add a new one for each "new" device it recognizes. So eventually you will have comm ports numbered into the teens even though you're not using them all. Some programs (particularly older ones) only recognize a limited number of comm ports -- and won't let you choose a high number such as "Com 14". In that case you need to determine which lower numbered ones are NO LONGER in use, and rename your AIS (or whatever) to use one of those numbers. Of course Windows will warn you that changing a number to one that is already reserved may cause problems, and you will make the choice to over-ride. These older programs are only reason I can think of to re-label ports, otherwise use "com 7" for AIS if your software supports it. It's just a name.

One tip -- Com 1 and Com 2 are more likely to be internal hardware devices than Com 3 (and higher). So don't choose Com 1 or 2 unless you absolutely must, as you probably will have a problem if a label you choose conflicts with devices that are still present.