Understanding Society User Support

We are trying to compute poverty indicators using both waves of the USoc. We have found that there is a significant increase in median income between waves 1 and 2 which seems unlikely. We want to try the analysis again without including the imputed income data. The variables a- and b_fihhmngrs_if, for example - which indicates imputation - have many values, but I can't find the documentation that explains what the numbers mean. Can you help?