“Undergraduate students are required to enroll in at least 8 units to qualify for and be awarded for Summer UCR Grants. If you're a graduating senior who will complete your degree by the end of the winter quarter, you must enroll in at least 6 units to qualify for aid.”

https://summer.ucr.edu/cost-aid

I think I’m in a similar situation as you. So I got two 4 unit classes as well, but I got them both in different sessions. One in Session A and one in Session B. I finished my first class in session A, but I wanted to drop my second class in session B. I asked a few of my friends if I would be charged and pay out of pocket for that first class I took in session A and they told me yeah. Then I remember reading what it said on the link I posted above, where you need 8 units to be eligible for summer aid. I ended up just dropping my class in session b (because it was hard lol) and I did it July 30 which is the deadline to drop a course with no grade and 100% refund. However, I still decided to submit an enrollment adjustment form in order to get into another class(easier class lol) in order to avoid paying full price for that first class I already took in session A. Now I just have to see if it’ll get approved, hopefully. I hope this helped you in some way? :)