I believe they are looking for “MMXV”
Really if you’re using Roman Numerals it should be MMDCCLXVIII AUC.
I mean if you’re going Roman, you should go full Roman and measure it ab urbe condita.
Actually it would be MMXV
No, Quartz Poker is right. It would be MMXV if you are going by Anno Domini, but the MMDCCLXVIII would be roughly accurate to Ab Urde Conditae, or the founding of the city and empire of Rome.