The big question is, what really do the event variables represent? Is that the terrain block currently being destroyed or something else? From my understanding of the numbers above, they don't fall within the area limits (the block positions anyway), but I am only barely understanding chunk and block positions. I assume that chunks are terrain chunks and block positions are positions within those chunks.
You are right, the blockposition is within a chunk. Chunkoffset is the global offset of a chunk. Chunks have a size of 16x64x16 (x,y,z) blocks.
The area above is outside the range: X and Z are within the area, but Y is at blockposition 56 (chunkoffset * 64 [chunksizey] + 56 == 0 * 64 + 56 == 56), but the area starts at Y blockposition 57 (chunkoffset 0), so 56 < 57 so it's not inside the area.