Here generally is not a timeframe involved in this. Is google penalized them then they received a manual penalty for unnatural links. They will have to identify all the links that are unnatural, contact all those site owners and try to take get the links taken down. Or disavow them and show a huge effort was made... And tell google that they won't do it again through a reconsideration request. Unless google makes an exception, it is taking at least five days or more for google to respond to RRs. And even then, once a penalty is lifted, the site won't necessarily come back quickly.