The inmates are allowed commissary once a week. The larger ticket items like TVs take up a huge percentage of the monthly spending allowed, so they have six month periods where the inmate can "overspend" to get these more expensive purchases and still get regular commissary.
https://www.inmateaid.com/ask-the-inmate/roxbury-correctional-institute-how-does-commissary-work-there-if-i-send-my-money-to-my#answer
Accepted Answer Date Created: August 01,2016