{ 1 } - true for all truth-possibilities of atomic propositions.
{ 2 } - not based on sense experience.
{ 3 } - empty in that it gives no information about the world.
{ 4 } - all of the above.

For example, "It is either raining or not raining" is true no matter what the weather is like. So it gives no information about the world. While it's a logically necessary truth, and quite certain, it's empty of content.

So Wittgenstein accepts that we have a priori knowledge of necessary truths. But he thinks that these necessary truths are trivial.