My son is 25 years old and is filing his own tax return. He is on my Marketplace plan. I need help in figuring out how to allocate the percentages when filling out my 1095-A. What happens if I claim 100% vs. 50%?

Also, he filed his taxes in February, but he has to amend them to include the 1095-A. How does he enter a 1095-A on his return when he never got one because he is on my plan?