It´s because that´s just a piece of my description. I was making a contrast. "He is 20 , but you could say he looks a litlle bit older ". Anyway, what I need to know is if it´s ok "he looks barely older" as an alternative to "he looks a little bit older " without a change in meaning to make it sound more formal register.
He's 20, but he looks a bit older.
He's 20, but he looks barely older.
In reality, I think we'd say, "He's 20, but he looks older." We will normally assume he looks perhaps 25, rather than 40. We won't think you mean that he's 20 but he looks 21 – we don't make those sorts of fine distinctions when we hear the sentence.