"Une" translates as both the indefinite article "a" and the number "one," and each can carry distinct implications depending on the context. Imagine a scenario in which the speaker is specifying how many pockets a certain bag has, not simply whether or not it has a pocket.
I see some people saying that it's more appropriate to use, "one pocket" instead of, "a pocket"; however, in the same exercise, "Il y a une petite chaussure" is accepted as, "There is a small shoe". Am I missing something?
'Le sac a une poche.' means 'The bag has one pocket.' while 'Le sac à une poche.' means 'The bag has a pocket.' the diacritical mark matters!!!