How to report field 55080 (or 5508)?
Field 55080 (5508 before 2019) is HBP repayment income. It is a supporting field for field 12900 of T1. It is used when you need to contribute RRSP to repay HBP, but you didn't contribute enough RRSP in tax year to repay it. So this part of HBP repayment shortage will be regarded as RRSP income.
Try to enter an amount into field 12900 of T1, it will pop up a supporting window. Field 55080 (or 5508) is the one for HBP repayment.