Admission is subjective. There is no way to quantify your chances of getting in unless your grades, resume, and life are above and beyond someone else’s.
A person with a resume such as this: 4.9GPA, 10 AP courses, 5 Honors courses, varsity athlete, awarded the Presidential Medal of Freedom, 700 hours of voluntering at a soup kitchen, and lost a leg while saving someone’s life
IS MUCH MORE LIKELY TO GET IN
than a person with stats like…2.8GPA, face tattoos, no volunteering, no clubs, no sports, no honors or AP courses, no nothing.
The above example is extreme, but that’s one obvious way to quantify someone’s chances of getting in. You, on the other hand, probably have a complex resume and life to the extent that no one can determine if that’ll get you into a UC or not.
3.78GPA, some volunteering, 1 junior varsity sport, 3 clubs, and won a fist fight against a 38 year old at a Walmart
VS
3.88 GPA, some volunteering, 1 varsity sport, 8 clubs, played piano for 3 hours in elementary school before your parents couldn’t afford it anymore, and know French fluently
The above two examples are the types of resumes and stat sheets people have when applying to UC’s. It is much more difficult to quantify the above people’s chances of getting in. If I were the UC admission committee, I’d go with the Walmart fight winner IF he wrote a killer essay explaining in detail how the fight transpired, who threw the first punch, the background of the area that they fought in, if any shopping carts were used (e.g. thrown, rammed, used as a shield, etc).
If you’re still reading, I did take 2 UCI extension courses while I was applying to UC’s, and I got into UCLA, UCR, UCI, and another UC I forgot about. Did it help me? I don’t know, but it didn’t hurt my chances…What I’m getting at is that it won’t hurt your chances unless you fail the courses. All it will do is help you more or less. As for how much? Beats me. It might be the deciding factor for all you know, and it might not be. If you are genuinely interested in the summer class/es, then take it. Don’t just waste thousands just to boost your chances of getting in.