Lesson 1: Multiple values used for 'size' parameter in MNIST demo

In the demonstration of different ways of labelling our dataset using MNIST dataset, the value used in the ‘size’ parameter was different each time. Could anyone please explain?

data = ImageDataBunch.from_name_func(path, fn_paths, ds_tfms=tfms, size=24,
    label_func = lambda x: '3' if '/3/' in str(x) else '7')
data = ImageDataBunch.from_csv(path, ds_tfms=tfms, size=28)
data = ImageDataBunch.from_folder(path, ds_tfms=tfms, size=26)

The values 24, 26, 28 were used on the same dataset.