Exports: How can a small amount of export make really high income
What you're asking1 stems from a more general question


  "How can such a small amount of some export $Q$ make the most money out of all the exports?"


To that the answer is to simply recall the standard formula for Total Revenue. 

i.e.

$$TR=P \times Q$$

Even though the quantity of export $Q$ is small it could be that the price for $Q$ (be that for whatever reason) be the cause for why it makes more revenue relative to the countries other exports. 

Hope this is helpful!  



1 I could be wrong