Per the rules of the Major League Baseball, for a player to gain Super Two status:
To qualify for the Super Two designation, players must rank in the top 22 percent, in terms of service time, among those who have amassed between two and three years in the Majors. Typically, this applies to players who have two years and at least 130 days of service time, although the specific cutoff date varies on a year-to-year basis.
If you are wondering how many service days a player must be on a Major League roster or disabled list to gain one year of service time, the answer is 172.