In ASEC, what does OI-OFF=1 (and OI-VAL) include that SS-YN and SS-VAL don't include?

In the CPS-ASEC, OI-OFF is a variable for Other Income, where 1=Social Security, 2=private pensions, 3=AFDC, et cetera up to 19 possible other income sources. OI-VAL is the corresponding $ value.

The CPS also has Social Security variables SS-YN and SS_VAL.

My questions are:

(1) What is the difference between SS-YN and OI-OFF=1? Do these variables include different forms of payment, eg. monthly benefits vs. lump sums? Is there potentially some overlap between these variables?

(2) Do respondents give a single answer to OI-OFF, or can they give multiple answers (eg., OI-OFF=1 for Social Security and also OI-OFF=5 for interest income)? If multiple answers are allowed, how is OI-VAL interpreted?

Thank you!

OI-OFF/OI-VAL are meant to be catch-all variables, asked at the end of the income questions to see if there was anything that the respondent missed in there initial responses. Respondents are only asked OI-OFF and OI-VAL once. This means that OI-VAL can be difficult to interpret since it does not necessarily correspond to OI-OFF (e.g. OI-OFF may indicate that they received other income from Social Security, but OI-VAL may contain income from Social Security as well as Rents and Royalties, or other minor income sources). The primary job of the OI-VAL variable is to complete the total income figure, insuring that all income sources were accounted for.

I hope this helps.