I’m sure you had billions when going into battle royale, but I’m guessing before battle royale you didn’t have the extra digit and afterwards you did. Unsigned int64 is 2^64 - 1 which equals 18,446,744,073,709,551,615. Notice it ending in a 5. Thus battle royale “wrapping” your score around.
The bug might still be there in .93… wait for the next code update and hopefully it’s fixed.