You can use whatever letters you like, as long as they match the PLAYERPKG value, and no one else shares the same PLAYERPKG value. The normal convention is first two letters of the first name, first five letters of the surname. So it would still be KECALDW and MICARTE, though again, it doesn't matter as long as it isn't already being used, and the filenames match the PLAYERPKG.
If there are conflicts (eg Jason and Jarron Collins), usually the first and third letters of the first name are used (eg JSCOLLI and JRCOLLI). Since TIHARDA is already being used for the senior Tim Hardaway, you could consider something like TIMHARD instead. Those are some of the common naming conventions, but you're free to make up your own, as long as the PLAYERPKG matches.