This spell works on creatures up to level @1

[Vapos]

Several spells on the wiki (stuns, Cajoling Whispers, lull animal, etc) show info that says "this spell works on creatures up to level @1". What does this mean?

I'm specifically curious about the Necro spell Rest the Dead. Allakhazam says it only works on undead below level 45. Is this true on P99? Does this spell not work on level 46+ undead? In HS South / East for instance.

Thanks