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 aToken = SToken(0x3FDA...);
uint borrows = aToken.totalBorrowsCurrent();
const aToken = SEther.at(0x3FDB...);
const borrows = (await aToken.methods.totalBorrowsCurrent().call());