Proposed $2,000 per adult + $2,000 per dependent (any age)
Additional under CASH Act: $2,800
As a single filer, you would have received $4,000 under the CASH Act (vs. $1,200 actually paid).
Next stepThe second stimulus check was an advance credit on your 2020 taxes. If you were eligible but received less than you should have, you could claim the Recovery Rebate Credit on your 2020 Form 1040.