Earlier this year word got out that the anime adaptation of Tokyo Ghoul manga sequel :re would cover up to chapter 56 which is the end of the Rose Investigation then news got out that the third season would only be for twelve or thirteen episodes. This has since been clarified by frequent anime/manga translator @YonkouProductions that the new season will actually feature two cours (or seasons) and will finish with a grand total of 24 episodes, or twelve per cour. Yonkou further clarified that cour two would air in October:

Tokyo Ghoul:re is actually 24 episodes split cour.

— YonkouProductions (@YonkouProd) April 27, 2018