Series had 31 to 39 annuals, depending on how one might count. There were originally 28 numbered annuals, running from 1964 to 1994. Annual was replaced in 1995 by a "Super Special." In 1996 annuals resumed but were numbered by the year in which they appeared ('96, '97, 1998, 1999, 2000 & 2001. The latter three annuals (1999 to 2001) are more accuratelty associated with Amazing Spider-Man (2nd series), though they are technically the same Amazing Spider-Man Annual (1st series).
Amazing Spider-Man (2nd series) resumed 1st series "legacy" numbering after #58 in 2003. In 2008, it resumed annuals and utilized legacy numbering. A total of 5 annuals between 2008 & 2012 were published th numbering #35-39. In 2014, Amazing Spider-Man (3rd series) was launched and in 2015 it had its own Annual #1, making that Amazing Spider-Man Annual (2nd series) #1. Subsequent Amazing Spider-Man annuals utilized #1s, complicating numbering schemes.