Complex sentence: The more complications in a watch, the more difficult it is to create, assemble and repair: typical date-display chronographs may have 250 parts, while a particularly complex watch may have a thousand or more parts.
Split into simpler sentences: The more complications in a watch, the more difficult it is to design, create, assemble and repair. A typical date-display chronograph may have up to 250 parts, while a particularly complex watch may have a thousand or more parts.