Theft damage, damage higher than half of the replacement value

Hello guys, I had a burglary damage in my Audi A4 convertible the other day. I was stolen the complete seats, Navi, Klimateil as well as Xenon headlights. My insurance company sent an expert of the Dekra and he determined that the replacement value is about 24,000 €. But the damage is about 12,500 € thus more than half of the gain value. The expert then told me that something would be deducted from the replacement value or something like that. I didn’t quite understand how you could explain this to me? Thank you very much!!