Final accounts December 2013

Hello Sir, I’m facing a problem in one adjustment from a final accounts question from a past paper.
Trial balance :
Insurance provision $150 000

On 1 October 2002 Moby received renewal quote of $400,000 from the company’s property insurer. The directors were surprised at how much it had increased and believed it would be less expensive for the company to self insure. Accordingly they charged 400,000 to admin expenses and credited the same amount to the insurance provision. During the year, the company incurred 250000 of expenses relating to previously insured property damage which it has debited to the provision.

In the answer they’ve simply reduced the admin expenses by 150000 I’m not sure why, can you please explain.
Thanks.