Okay, so what about finishing the granary at 22/36 and then adding 14f? Is that only 14/38?
Yes. If you could run 13f for a turn you'd go:
22/36 Granary done
35/36
31/38 (18 max granary food, + 14-1 = 13 overflow).
EDIT: Or avoid growth for a turn, to get 32/38.
That compares with 28/38 running 14f straight, but the latter grows to size 9 a turn sooner and works one extra tile as a result.