There is a point at 4 and a blue arrow goes to left from that point. Write the set of numbers represented on the number line in interval notation.

Please directly answer the question and provide the final value, e.g., 1, 2.5, 300.
Question: There is a point at 4 and a blue arrow goes to left from that point. Write the set of numbers represented on the number line in interval notation.

Please first conduct reasoning, and then answer the question and provide the final value, e.g., 1, 2.5, 300, at the end.
Question: There is a point at 4 and a blue arrow goes to left from that point. Write the set of numbers represented on the number line in interval notation.
