Is he over age 25? If so, he probably received a higher EIC in 2019. His total income was lower in 2020, and Unemployment Comp does not qualify for EIC. Even if not, his 2020 total was about $1,000 less than 2019; but is taxes withheld were also $1,000 less.
Look at his 2019 and 2020 tax returns side by side. Something may stand out.
