What happens when you add hay cubes to a box?

Hopefully, this riddle is not too taxing.

Everybody checking out the fresh hay cubes.

Lucy fairly quickly decides three's too crowded,
picks up one of the largest cubes
and hauls it off back to the pen to enjoy by herself.
(And, by the way, she was too close to a human;
if she got too distracted by the treat, she might get picked up.)

Ethel and Bunya remain in the box and
share the other really big hay cube.

Later, Bunya discovers the treasure Lucy left behind,
just slightly smaller than before.