The poster is talking about post-sentencing "discounts" on prison time served. It's called Good Conduct Time or "good time" for short, in Texas. The way it works is that prison administrators offer inmates early release based upon their behavior. It's a very important and useful prison management tool, one of the only carrots that prison administrators have to offer inmates.
If you follow the link, you'll see that participating in work or educational programs can improve one's good time earning class, allowing an inmate to earn an earlier release date. In contrast to the other poster, Texas requires good time for time served in county jails. Also notable, educational opportunities have been severely curtailed in TDCJ over the last decade.
Source, was a CO in Texas, also: http://law.justia.com/codes/texas/2005/gv/004.00.000498.00.h...
If you follow the link, you'll see that participating in work or educational programs can improve one's good time earning class, allowing an inmate to earn an earlier release date. In contrast to the other poster, Texas requires good time for time served in county jails. Also notable, educational opportunities have been severely curtailed in TDCJ over the last decade.