Why only partial refund for defaced note?

I submitted a $10 currency note with one of the edges slightly torn and parts missing to DBS Bank recently.

I did not realise that I could not simply exchange the partially defaced $10 currency note for another $10 currency note.

I was instructed to fill up a form with my personal details and a narrative of how the defaced $10 currency note came to be in my possession.

After I submitted the form to the bank, I was told to wait for further investigation by the currency board before I would know whether I could have a replacement amount of $10 credited to my savings account.

I was sorely disappointed to learn that the currency board could credit only half the amount - that is, $5 - to my account.

No reason was given for the penalty in submitting a partially defaced $10 currency note for full exchange.

Could the currency board authorities give a good reason for the partial refund? It was not my fault that I had in my possession a partially torn currency note.

Kwie Siew Wah