It looks like Standard competition ranking or 1224 ranking is applied on the leaderboard where if multiple folks are ranked the same, the next spots are skipped.
In competition ranking, items that compare equal receive the same ranking number, and then a gap is left in the ranking numbers. The number of ranking numbers that are left out in this gap is one less than the number of items that compared equal. Equivalently, each item's ranking number is 1 plus the number of items ranked above it.
This doesn't look like a bug.