There are buses from Radda to Florence, but there are more frequent departures from Greve. The schedules are here:
The schedules into Florence start on page 6. There are only two morning departures from Radda, but buses leave several times an hour at peak times from Greve. The trip takes a little less than an hour.
You have to pay attention to all the notes and little symbols. The SAB at the top of some columns means the bus runs only on Saturdays. The numbers at the top indicate either extra stops or the dates that the bus runs. For example some buses run only in the summer and others run the rest of the year. You can see the dates in the footnotes even if you can't read Italian; remember that in Europe the date is written day, then month. "giorni scolastici" means when school is in session.
In addition, there are symbols in the columns with wavy lines connecting them. The crossed hammers mean working days, which is Monday through Saturday. The cross means Sundays and holidays. I have no idea what the A means. I suspect it means every day, but on most bus schedules, that's indicated with a G (giornaliere).