The best approach with individual machine licenses (as opposed to site licenses) is to create a software item instance for each license. If you purchase a 5 user pack of FileMaker for example, you will receive 5 different license codes.
Go to Software Detail and create the first license, then duplicate it 4 times using Duplicate Software from the Software menu and entering the unique license code for each instance. Now assign each of these to the appropriate computer from the Software Detail page for example. HSTracker tracks software items with different license codes as separate entities, as they should be.