It the number of the coin issued in that series. Coin 1 in the Lincoln series was the 1909-P, and that number counted up for each date/mint combination issued. PCGS abandoned that method of identifying coins several years ago.
Yes Lincoln cents were series 14 and the coin number related to which coin it was in that series. PCGS still uses those numbers internally. They had intended for people submitting to use them as well but it never caught on. PCGS listed the Series and Coin numbers on the slab labels from Jan 1990 to November of 2005.