Maybe just the actual recording process? As in they had all the writing and beats all prepared and in 20 days JT provided all the vocals?
There's so much involved when putting together an album, but I doubt he'd lie about it. There's nothing really to gain from claiming you cooked up your album in 20 days besides maybe bragging rights and for the fun of using the number 20 again? I don't know if people hear that and are like "woah I love albums recorded in less time it to complete a menstrual cycle!"