Its very possible that you client has a payback if their income was higher in 2020 than what they told Covered California it would be. Ive had clients that have saved this payback by putting money in an IRA, so that's the first thing you should look at, do they qualify for an IRA?
Last year I had a guy that was going to have have to payback over $8000, but by putting $825 into an IRA (I worked the program, trying different amounts, until I found the lowest dollar amount that would get his income below the 400% poverty level), and reduced his payback to 1125 and only ended up owing $200 on the return, so it can be a huge savings tool if they qualify. They have until 4/15/21 to get the money into the IRA for it to count on the 2020 return.
To find the 3895 in the CA return, hit CTRL+F and type in 3895