Yes , the first numbers are depth size,,,,,,,the "K" is a series of joist that had replaced the "H" series in 1986,,,,,,,,there's a "KCS" series joist that fits the need when constant moment and constant shear (special loading conditions) come into play.....
The last number designates cord size (top and bottom back to back Angles),,,,,,,as Mr. Norris had mentioned , its a simple scale created by the SJI with its own strength values,,,,,2 being stronger than 1 ,,,,, 3 being stronger than 2,,,and so forth....
if i were you , I'd figure out what's needed and duplicate it........