OP is Italian. The u in the Italian word for university, universitá, is said with a vowel ‘ooh’ sound instead of a consonant ‘you’ sound. I’d wager they remember their English ‘a vs an’ rule phonetically and, with the words being so similar between languages, mixed the pronunciation up. I’m a native English speaker and that’s 100% how I fuck up my Italian.
That’s how my milk used to come when I was a little kid.