Assuming there are three people listed on the 1095-A, (you, the other parent and the child) your allocation as 33% each (with one obviously getting 34% so things total to 100%)
So if the other parent paid for the child's portion, you'd only claim 33% for yourself, leaving the remaining 67% for the child and other parent.
If you paid the child's portion, then you'd claim 66% if you were the custodial parent as defined by the IRS, weather you actually claim the child or not.
