What is referred to by 'at 30'?

Based on the clue 'at 29 feet 4 12 inches mike powell holds the world...', what is the answer? Based on the clue 'at 3 12 million square miles this largest desert c...', what is the answer? Based on the clue 'at 3 times proportional size of any other primate ...', what is the answer? Based on the clue 'at 30 years this pbs series from the austin music ...', what is the answer? What is associated with: at 3031 miles in diameter this planet is the second smallest in our solar system? Based on the clue 'at 306 feet high the bennington battle monument in...', what is the answer? What is referred to by 'at 311'? What is associated with: at 3110 feet tugela falls in this countrys kwazulu natal province is the worlds second highest?