[Dan Theman]

Interesting side notes (and reasons why unofficial summaries on websites are often incorrect) -

According the the CBA:

If a Player is optionally assigned for a total of less than 20 days in one championship season, such optional assignment(s) shall not count as an optional assignment in connection with the limitation upon optional assignments provided for in Major League Rule 11(c). (See Article XXI(B).)

For purposes of counting days on option, the date of the optional
assignment shall be counted and the date of recall shall not be counted, provided that the date of recall shall be counted if the recall takes place after the start of any Minor League game in which the Player was eligible to play.

According to Rule 11 of the Professional Baseball Agreement, which governs the transactions between the major and minor leagues, optional agreements "shall be permitted for not more than 3 seasons between Major League Clubs and National Association Clubs (minor league affiliates), and three seasons between National Association Clubs; provided that if a player is optioned for less than 30 days in one season, as determined by the date of the optional assignment and recall, respectively, that shall not count as an optional transfer in connection with the foregoing limitation." However, if a player has less than 5 seasons professional experience, he is eligible for an additional option. After he's used up his options, a player must clear general waivers to be designated. The number of options transfers if he is traded but does not reset.

Padre GM Kevin Towers explains it further: "A player has three options, and optioning him means taking him from your major-league roster down to your Triple-A roster, or Double-A or Single-A roster. You can send a guy up and down as many times as you want, and it only counts as one option in a year. After you've added a guy to the major-league roster, you've got three option years - if you option him down once in every year, then he becomes out of options. Once the player's out of options, it means to get him to the minor leagues you'll have to send him through outright waivers."

According to a couple of minor league ballclub websites (and, as it turns out, ESPN - I wonder who printed it first?):
"After a player has played three full professional seasons, he must be protected on the Major League Team's 40-man roster or he becomes available to be selected in the Rule 5 draft. If after the three years he is placed on the Major League Roster, the club then has options on that player. A player on the 40-man roster but not on the 25-man Major League Roster is on what is called optional assignment. A player on optional assignment has three option years, and can be sent up and down as many times as the club sees fit during those three seasons. A player who has been in the Major Leagues for parts of three different seasons is out of options, and must clear waivers in order to be sent down beginning with his fourth big league season. "

Are we confused yet?