“Yet you have not walked in their ways nor done after their abominations, but, it is a very little thing, (or ‘in a very little time') you were more corrupt than them in all your ways.”
The statement is sarcastic. They had not behaved like Sodom and Samaria, no, they had behaved far worse. Sodom and Samaria were bad enough, but Israel had sinned even more. ‘It is a very little thing' is probably the intended meaning and is heavy in sarcasm. ‘A little thing' was how Israel might have stated it, but not Yahweh. (The translation ‘In a very little time' would suffer from the fact that Sodom's history was long past, even though such lengths of time were then probably very vague to most people).