According to my dictionary: adv. Thus; so. Used in written texts to indicate that a surprising or paradoxical word, phrase or fact is not a mistake and is to be read as it stands.

So, without more context we really don't know to what the second writer was referring with the "sic". However, the "estimate" belongs to the singular or plural "reporters" but we can't tell without the apostrophe positioned correctly to indicate possessive form.

Also, if there is more than one reporter, did they each have an estimate, in which case the word "estimate" should be plural? Or did they all huddle and come up with one estimate? Need more info to really know.