The falling leaves formed spirals in the air, like the spirals I saw when I did divisions in my head.
What is the meaning of the last sentense? (I don't understand the underline word and sentence)
The entire text can be found here: Born On A Blue Day: Inside the Extraordinary Mind of an Autistic Savant - Daniel Tammet - Google Books
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.