Index in categories_mean

Hi,
Sorry if this has already been covered, how does this function below work? Specifically, the [0] index at the end of the line
if price < genres_mean.loc[(aff, gc)][0]:

Many thanks,
David.

def label_genres(row):
“”“For each segment in genres_mean,
labels the apps that cost less than its segment’s mean with 1
and the others with 0.”""

aff = row["affordability"]
gc = row["genre_count"]
price = row["Price"]

if price < genres_mean.loc[(aff, gc)][0]:
    return 1
else:
    return 0

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