A little confused about a sample answer to a question about audit risks

I was practicing a question about audit risks and auditor’s responses and this sample answer to the question left me a bit confused.

This was the scenario:
“Harlem Co sells approximately 40% of its tyres to wholesale customers. These customers
purchase goods on a sale or return basis. Under the terms of the agreement, wholesale
customers have 60 days during which any returns can be made without penalty. The finance
director has historically assumed a return rate of 10%, however, he now feels that this is
excessive and intends to change this to 5%.”

This was the sample answer identifying the audit risk:
“The finance director is planning on reducing the estimated return rate for goods sold on a sale or return basis to wholesale customers from 10% to 5%. IFRS 15 Revenue from Contracts with Customers provides that revenue and cost of sales should only be accounted for to the extent that the company foresees that the goods will not be returned. For the goods which may be returned, the company should recognise a refund liability. If, after 60 days, the goods are not returned, then this liability is reversed and revenue is recognised. By reducing the return rate, there is a risk that revenue and cost of sales may be overstated and liabilities understated.”

While I understand every other part, the last sentence had me puzzled. If the return rate had been reduced, wouldn’t that mean the refund liabilities accounted for using the original 10% return rate would be *overstated* and the revenues and costs of sales recognised would be *understated* because the return rate will be reduced to 5%?

I feel quite stupid not understanding this, and I never really was an expert with IFRS 15 when I had my F7 exam. I’d really appreciate it if anyone could help me understand what the sample answer wrote!