You entered your GPA correctly. They want to know your 10-12 on the application, but Cal Poly SLO will recalculate like gumbymom said.
Send in both of your ACT scores. They will take all of your highest subscores and create a new composite score
For Example:
Test 1: 27C (18E 18M 36R 36S)
Test 2: 27C (36E 36M 18R 18S)
Superscore: 36C (36E 36M 36R 36S)