It's pretty common in English too, especially when ordering something.
"What would you like to order?"
"I'll have two coffees, thanks."
liten is an adjective meaning small and has endings depending on if the substantive is an en- or an ett-word. lite is an adverb meaning little or some.
- Kan jag få lite kaffe? - May I have some coffee?
- Kan jag få en liten kaffe? - May I have a small coffee?
- Kan jag få ett litet äpple? - May I have a small apple?