My game just glitched to the max

Ok, so there have been some minor glitches here and there, but after what just happened to me, there’s no contest.
Details: So with the Halo 5 beta coming out I finally decided to watch Halo: Nightfall, because I didn’t have time to do it in the past. I watched all five episodes and found out about the rewards you get for watching them. I was glad to see I got 8/8 rewards, one of which caught my eye. The swarm skull for Halo 2. I clicked on the swarm skull reward on the Halo Channel and it directed me to Halo MCC, where the glitches began. When I entered the main menu, I randomly received 7 achievements I shouldn’t have gotten, one of which was to complete 800 missions. Now, I knew I didn’t play 800 Missions, I don’t even think I’ve played 30, but it unlocked. It also gave me the achievement for completing Halo 2 on Legendary, which I didn’t, I’ve only completed Halo 2 on Normal. Confused, I went to my service record to actually see how many missions I completed. Sure enough, my stats also glitched. It says I’ve completed 809 missions and have spent over 2400 hours playing the campaigns. These are not true to the slightest. It also says I’ve spent 296 hours playing Halo 2, also false. This is a glitch. I am posting here because I want to confirm just in case, if anyone looks at my MCC service record, I did NOT tamper, hack, or modify the game at all or in anyway possible. I was simply watching Nightfall, got my rewards, went to MCC, then got glitched to the max. Has this bug happened to anyone else? And if possible, I’d like my stats to return to normal.

That’s crazy. Too bad it didn’t give you the LASO achievements !

Ha, I don’t even know what I’d have done if that happened. I just don’t want people to think I cheated, because I didn’t.

did the skull unlock for you? because its not for me