"cidden" is kind of more exaggerated than both "really" and "very." It is kind of like the what that English speaker say "the sandwich is seriously delicious." It is closer to "really" is suppose, but it is stronger than that.
In this comment, the word 'really' meant 'very' as we commonly use in English. The hints also indicated 'çok' ie 'very' was an option which would be correct, but the answer was marked as incorrect. I thought 'gerçekten' in speech meant 'really' as 'factually'.