South Carolina SSP 2017, 2018, 2019

The South Carolina SSP is calculated as "The federal SSI payment and any countable income are deducted from the state standard. The remainder is the state supplementation." (https://www.ssa.gov/policy/docs/progdesc/ssi_st_asst/2011/sc.html)

For 2017, the monthly net income was $1,420, and the Federal payment amount was $735. This means the state supplement was $685.
https://apps.sceis.sc.gov/SCSolicitationWeb/attachmentDisplay.do?attachName=PL+006+Program+Financial+Limits&attachType=PDF&dateModified=05%2F15%2F2017+04%3A56%3A55+PM&phioClass=BBP_P_DOC&phioObject=005056AC04D71ED78EB59AD09FA24116&solicitNumber=5400013203&type=S

In 2022, the monthly net income was $1,526, and the Federal payment amount was $841. This means the state supplement was $685.
https://www.scdhhs.gov/sites/dhhs/files/documents/Medicaid%20Eligibility%20Groups%20Effective%203.1.22%20Final.pdf#page=3

This means for 2017, 2018, and 2019, the South Carolina SSP was $685.

SSI Federal Payment Amounts: https://www.ssa.gov/oact/cola/SSIamts.html