I too have noticed a change in the audio since I posted my comment. Unfortunately they seem to have overshot the mark. It no longer sounds like she's saying "una" when she should be saying "un," but now it sometimes sounds like she's saying "un" when she should be saying "una"!!!
I think that's probably true in our native language without our realizing it. We could hear: "Ahm gonna go cuz I dint eat yet." and we would write: "I'm going to go because I didn't eat yet." (Well, ok it should be "haven't eaten" but it wouldn't be so funny.) Dumb example, I know, but my point is that when we know the meaning the pronunciation doesn't put us off. And if everything we hear in Italian was well enunciated we'd be lost in a real life situation. Gada go now. ;)
Idiomatically in English "A quarter of the whole" sounds better to me than "A quarter of the total" -- the latter feels like it needs completing with something like "... the total amount". Small point, but I'm not clear why "whole" is marked as incorrect. And being a British English speaker I can't imagine saying "a fourth" in this context!