Can someone please explain to me the second paragraph on schedule 8812 (What's New) which read,

"Earned Income figured for additional child tax credit.  Recent legislation for 2020 allows an election to use prior year earned income when figuring the additional child tax credit. see line 6a"  I have a client that have 3 children but made only about 7000 in 2020.  My question is, does the above statement means I can use his 2019 income (25,080 ) this year instead of his 7000 income in 2020.

Thanks