As Mr. Tsang said in his opening remarks, the vast majority of student loans are repaid to the government over the lifetime of the loan. The exact number is about 87.2%.
Taking that another way, almost 13% of loans are not repaid. Of that amount, about 11% is written off, so a writeoff of $149 million is captured in the request to Parliament under these supplementary estimates (B).
The government forgives very small amounts—the difference between 11% and a bit, and 13%—because of the death or severe permanent disability of the borrower, or because, as I had answered in response to a previous question, the borrower is on the repayment assistance plan. While they're on that plan the government may be paying down or forgiving part of their principal. Those are the reasons for the 13% of loans that are not repaid to the government.