Coniunctivus has got many functions in Latin, jairhaas. It can express possibility, wish, supposition, order...
I've proposed to translate the sentence by "possibility" (coniunctivus optativus), because,without context,it seemed to be the best option.
Anyway, I think that "should be" is possible here too(it would be "coniunctivus iussivus" expressing an order...).