SQL Error Code: 1172 on update not insert

Question

I have a very basic query here

UPDATE leads
SET created = NOW()
WHERE id IN(
    4142429,
    4142430,
    4142431,
    4142432,
    4142433,
    4142434,
    4142435,
    4142436,
    4142437
);

But whenever i try to run it in sqlYOG, I get the error:

Error Code: 1172
Result consisted of more than one row

I did some research to the error, and that turned up this question:

Error 1172 : Result consisted more than one row (in SQL)

which has already been answered, but the answer is not clear. I'm not inserting anything into the table either.

I have also tried doing the query

UPDATE leads SET created = NOW() - INTERVAL 1 DAY WHERE ID = 4142432;

But I still get the same error.

Why does this happen when I am only updating one row?