Fixes land, and the index starts reflecting them
Weeks 1 to 4Technical corrections take effect as fast as Google recrawls, which on an established site is often days. Blocked pages become crawlable. Broken canonicals stop pointing at the wrong URL. Pages that were invisible for configuration reasons can reappear quickly, because nothing had to be earned, only unblocked. This is the only phase where dramatic movement is normal, and it happens exactly when the original problem was self-inflicted.
What to watch: Crawl rate and indexed page count in Search Console