Per IRS Instructions for Form 1040A, page 61:

Excess social security and tier 1 railroad retirement (RRTA) tax withheld. If you, or your spouse if filing a joint return, had more than one employer for 2018 and total wages of more than $127,200, too much social security or tier 1 RRTA tax may have been withheld. For more details, including how to figure the amount to include on line 46, see Pub. 505. Include the excess in the total on Line 46. Write “Excess SST” and show the excess amount to the left of the line.