The cache is located at the indicated coordinates.
You may sign the log at anytime, but you cannot claim a "find" unless or until you qualify for this challenge.
In order to qualify, your cumulative elevation for all of your found caches as you travel from cache to cache, must meet or exceed the FAI qualification of 100 kilometers/62 miles (100,000 meters or 328,084 feet).
Project GC has provided a checker to make the task of showing your qualifications much easier. To prove your qualifications, simply cut and paste the confirmation from the Project GC checker in your log. Cache on!
Since I would never publish a challenge cache I don't qualify for myself, Project GC says I have travelled 320,668 meters or 1,052,060 feet of elevation.