I think you didn't get through because you didn't actually say that, infact you said something completely different
part files = a single file as it was intended
chunk = a chunk of a part file.
You seem to be calling chunks, parts, which they aren't. 70 part files is 70 different files (ie. 70 different downloads) that don't go together in the first place, 70 chunks = 70 chunks of a single part file, which i now take it you mean?
Anyway, never even heard of a part file exploding into its single chunk pieces but that's what you get for using redundant software tell him, he's going to have to append them all in nandub manually.