Total Borrows is the amount of underlying currently loaned out by the market, and the amount upon which interest is accumulated to suppliers of the market.
SErc20 / SEther
function totalBorrowsCurrent() returns (uint)
RETURN: The total amount of borrowed underlying, with interest.
SErc20 sToken = SToken(0x3FDA...);
uint borrows = sToken.totalBorrowsCurrent();
const sToken = SEther.at(0x3FDB...);
const borrows = (await sToken.methods.totalBorrowsCurrent().call());