Green’s Dictionary of Slang

get up v.2

[get-up n.3 (1)]

(US prison) to reach the end of one’s sentence.

[US]J.L. Kuethe ‘Prison Parlance’ in AS IX:1 26: get up. To finish a prison sentence.
[US]Monteleone Criminal Sl. (rev. edn).
[US]P. Crump Burn, Killer, Burn! 287: I just got up from doing a ninety-day bit at the County.
[US]‘Iceberg Slim’ Airtight Willie and Me 39: Sugar Babies, most of you are hip that I just got up from a fall.
[US]L. Bing Do or Die (1992) 22: I’m lookin’ forward to gettin’ up outta here. I been here four months.