I used to have very low reputation (lower than 20). But suddenly, when I came on this site a few days ago, my reputation suddenly went up to 151. How did that happen? There was no notification, and there was nothing in the reputation history that could explain this. It's not that I don't want the extra reputation, I would just like to know where it came from.
Reputation changes from deleted proposals eventually "age out" of the system. The massive reputation loss you had from posting a series of bad suggested questions has finally expired, giving you back the default 50 rep (from verifying your email) and the extra 100 rep (from your StackOverflow account being above 200 rep).
You have more then 800 rep at StackExchange https://stackoverflow.com/users/4356188/narawagames that gives you 151 rep when you sign into Area51.
Rep varies by site. http://stackexchange.com/users/5479133/narawagames?tab=accounts
You can read more about rep here https://stackoverflow.com/help/whats-reputation
Everyone starts with 1 rep when they log on for the first time. When you get to 200 rep on anyone site, you automatically get 100 extra rep at every other site.