Approximately is close to a particular time, measurement, or number — but it's not exact. If you plan to meet a friend at approximately 2:00, it will be okay if you are a bit early or late.
Approximately has its roots in the Latin word proximus, meaning "nearly." So, approximately means "about" or "close to." If you tell someone there will be approximately seventy people at a dinner, it means you expect seventy people, though the actual number could be a little more or a little less than seventy.