In general, "landward" means "closer to, or in the direction of, the land," and "seaward" means "closer to, or in the direction of, the sea" - "As I stood on the beach facing seaward, a stiff wind blew into my face and carried the rain landward from the sea." In your context, it helps to know that the "seaward boundary of a state" is the imaginary border line across an entrance (such as a bay or river mouth) separating inland and offshore waters - "A boat that capsized seaward of the boundary was in offshore waters for the legal purposes of insurance and international maritime regulations. Another boat, which foundered nearby in the same storm, was found to be landward of the boundary and was subject to local laws and inland water regulations."

seaward = towards the sea (away from land) landward = towards land (away from the sea) So, in this case: (i) $35,000,000 for an offshore facility located farther from the coast than the seaward boundary of a State; or (ii) $10,000,000 for an offshore facility located closer to the coast than the seaward boundary of a State. The seaward boundary of a state is just an imaginary line (like a state line) that is a certain distance off the coast of a state.