[Lord Plothos]

The table has a 0 instead of a 1 to indicate that you only get to cast spells there if you get a bonus spell from a high wisdom. The number of spells per day equals the number on the table plus any bonus spells. So a 0 there means you get just the bonus spells. A dash, or a no-entry means you don't even get any bonus spells.

And, as always, in order to cast spells of level X, you need your relevant ability score (wisdom in this case) to be 10+X.

A paladin with a wisdom of 14 gets one 1st level bonus spell, so at 4th level, he gets 1 1st-level spell per day (just his bonus spell). At 6th level, he gets 2 per day (one for being a 6th level paladin with enough wisdom to cast 1st level spells, and one bonus spell for high wisdom).

A paladin with a wisdom of 11 at 4th level has no 1st level spells to cast. But at 6th level, he gets 1. Unless he raises his wisdom, he won't be able to cast 2nd level spells, as this requires a wisdom of 12 or more.

A paladin with a wisdom of 8 can't cast spells at any level, because his wisdom is too low.

That's how D&D 3.5 works, anyway. I'm not sure I remember correctly, but I think ToEE has issues here. Normally they get this right, but if you boost your stats with things like periapts of wisdom, you won't get bonus spells for it. (In 3.5, if you wear it continuously from resting through preparation, you do get bonus spells for improved ability scores.)