Kill Reset is used with sequential spawning. Its kinda like champion spawns keeping track of kills during progression and how it resets and back tracks. Xmlspawner doesn't backtrack like the champs do. When using sequential spawning you can set a number of required kills for a mob sub group in the sequence. Kill Reset is how long the spawner keeps track of kills before it resets to zero. So if you have your required kills set to 100 you will want the Kill Reset set high enough to make it possible, depending on your aim with your sequential spawn you can have it barely possible or just set the Kill Reset Super high so it doesn't reset for days. I hope that answers your question well enough.