To qualify for this challenge you have to find caches in at least 10 different counties.
Country doesn't matter.
10+ different cache types in one county.
9+ different cache types in a 2nd county.
8+ different cache types in a 3rd county.
7+ different cache types in a 4th county.
...
1+ cache in a 10th county.
That means you have to find a total of at least 55 caches, at least 10 different types and at least 10 different counties.
This is a challenge cache
A challenge cache means that the container is at the posted coordinates, but to be able to log it as a find you have to fulfill certain requirements.