I was on my parents marketplace healthcare plan from January to August. I was then enrolled through my employers insurance starting September. 

My parents never removed me from their plan.

I have a 1095-A (Jan-Dec) and 1095-C (Sep-Dec).

How do i properly report this as i'm getting substantially charged due to my parents plan. 

Are there specific ratio's i should be using when asked 

"What percentage of the following policy amounts do you want to claim on your tax return?"