Comment by gus_massa

They show whatever they want to show. For example see https://www.google.com/search?q=matemathica If you search for "matemathica" they will show the results of "mathematica" instead, and offer to search for the original word. Sometimes they mix the results of the original word and the autocorrected version. Sometimes they show the results of the original and offer to show the results of the autocorrection.