Please click on the RRSP tab and select HBP
Make sure your box is checked.
On the next page you can enter the balance to be repaid, the required repayment but for the next box "Enter the amount you wish to designate as a Home Buyers' Plan repayment", enter 250 only.
This should get rid of the error. Warnings do not prevent netfile. You will likely still have a warning but can ignore it.