1. Caster level
2. Target level
3. Sleep level
4. Last level of sleep learnt (maybe u can learn sleep lvl 13 but u only have sleep lvl 11 on u .. so that will obviously make a difference)
5. Caster INT
6. Target's sleep resistance (if he has aegis on him or whatever else that increases resistance)
7. Caster Matk
8. Target Mdef
This one is NOT applicable to mobs right now (since all mobs have same stats as far as dex, con, str, etc go)
9. Target WIT (resistance to sleep)

so .. 9 is only applicable to l2pcinstance