I assumed that I would be able to update it durring the supplemental application, but that only lets me update fall of 2019, winter of 2020, and spring of 2020.
Any idea of what I could do or what would happen? It was a non transferable course if that matters.
Since it was before fall 2019 you need to email the UC and tell them the grade. They need it to calculate your accurate unit count as well as cumulative GPA. Leaving it as is will make them assume that you dropped it. It should have been listed in the November application. Email them at docs@applyucsupport.net