Why does auto increment jumps by more than the number of rows inserted?

I am very perturbed by this weird behaviour I am seeing in the auto_increment value recorded in the bidID of a Bids table after performing bulk insertion using a stored procedure: INSERT INTO Bids (itemID, buyerID, bidPrice) SELECT itemID, rand_id(sellerID, user_last_id), FLOOR((1 + RAND())*askPrice) FROM Items WHERE closing BETWEEN NOW() AND NOW() + INTERVAL 1 WEEK ORDER BY RAND() LIMIT total_rows; For example, if the auto_increment bidID value is 101 at start, and I inserted 100 rows, the ending value becomes 213 instead of 201. However, the bidIDs of those inserted rows runs sequentially to a maximum of 201. Having check the following, SHOW VARIABLES LIKE 'auto_inc%'; +--------------------------+-------+ | Variable_name | Value | +--------------------------+-------+ | auto_increment_increment | 1 | | auto_increment_offset | 1 | +--------------------------+-------+ I have no idea why it is happening. What could be causing the jump in the auto increment value?