We know that Agostino reaches Rome "on the fourth day after setting
out" (Chapter 4.VII) and, on that same day, Galeotto reaches Pagliano
and starts immediately for Rome. Presumably he arrives a few days
later and frees Agostino instantly; we know this happens on September 3.
Agostino's statement that he "had not seen [sunlight] for a full week"
(Chapter 4.IX) is impossible; Galeotto cannot have taken a week to free
him. We conclude that Agostino meant to say that he was in the hands
of the Inquisition for a week, and therefore was taken August 27.