UCLA does not admit by major into the College of Letters and Sciences so the 10% admit rate is the overall admit rate for that College. Actually the new 2023 numbers are out so the admit rate is now 11% but UCLA the College of L&S had 95,967 applicants and admitted 10,420. Since UCLA does not admit by major, once admitted the students can pursue any major by just completing the required pre-req courses to declare. UCLA’s overall campus admit rate was 9% with 145,910 applicants with 13,747 admits.
In contrast, Cal Poly SLO admits by major and has less capacity for the number of students that they will admit into their programs.
SLO has target projections for each major so they expected 3579 applicants for the 73 spots available in Psychology. They will admit more students than spots since not all admitted students will commit. Cal Poly SLO’s overall campus admit rate was 29.7% with 63,958 applicants and 18,964 admits.
Admit rates are just another data point but you need to look at the context. The GPA ranges quoted for UCLA is the 25th-75th percentile for the entire campus. The SLO GPA is the 25th-75th percentile for the College of Liberal arts where Psychology is housed but not for the entire campus. SLO GPA also uses 9-11th grades where the extra grades added to the Honors point cap dilutes the weighted GPA.
I hope this information gave you more perspective.