Negative-energy-charged creature: Hard to hit, or really hard to hit?

[draykhar]

So I was browsing through the advanced Bestiary, when I came across the Negative energy charged creature. It seems really flavorful, very powerful, but I was looking at Obscuring energy, and I can't tell. Is the miss chance 20%, or 50%?

Obscuring energy text:

Obscuring Energy (Su): Black negative energy plays about the body of a negative-energy-charged creature, obscuring its form and providing it with concealment. Thus, attacks against it suffer a 20% miss chance, and it can hide behind its energy "shield" when unobserved. This negative energy takes the form of a black cloud and is thus easy to locate in normal light, but it still grants the negative-energy-charged creature total concealment (50% miss chance) and allows it to make an attack from hiding.

[Isil-zha]

50% if it managed to hide while unobserved, 20% otherwise

basically even when hidden it is easy to locate because of the black cloud, but it has total concealment because you cannot see the creature, just the cloud