The 4th Option Year
In some circumstances, baseball rules allow for a fourth option. A player receives a fourth option if he has less than five seasons of pro experience. Draftees who immediately sign a major league contract will qualify unless they reach the majors quickly and stick there. Otherwise, they'll have their three options exhausted after their first three years in pro ball. Guthrie falls into this category.
A season is defined as any year in which the player spends 90 days on the active list. Short-season and Rookie leagues don't last 90 calendar days, so a player assigned to those leagues for an entire year won't accrue a season of pro experience. Also if a player has a long-term injury, he usually won't be credited for a season that year. (The exception is if he goes on the disabled list after spending 60 days on an active list, in which case the DL time counts as service time.)
Aubrey was drafted and signed in 2003, and he was active for less than 90 days in 2003 so it does not count as a season. 2004 is a season played, but he missed most of 2005 and 2006 and they do not count. 2007 and 2008 are his other two seasons, so he has only three seasons (2004, 2007, 2008) which is why he will get that fourth option this year.
Sipp was drafted and signed in 2004, but that season does not count as a played because he was in short-season ball which is less than 90-days long. 2005 and 2006 count as seasons, but he missed all of 2007 with Tommy John surgery and missed most of 2008 with the injury and was on a rehab assignment the rest of the year so it does not count as a season. 2008 was his first option year, so assuming he uses his two remaining options in 2009 and 2010 and is healthy, that would only be four seasons played (2005, 2006, 2009, 2010) so he would get the fourth year option if needed.