fCash residuals refer to an nToken’s net fCash position after converting its liquidity token holdings into their constituent cToken and fCash components. If an nToken account is a net borrower (if end users have been net lenders) it will hold a negative fCash asset position or what we call "negative residuals". Conversely, if an nToken account is a net lender (if end users have been net borrowers), the account will hold a positive fCash asset position or have "positive residuals".