It depends on the violation, the judge hearing the case and if it's the judge that originally sentenced them the re-sentencing could be quite harsh. The time could be a few weeks and all the way up to the entire amount of the sentence that was remaining when they were granted parole.
https://www.inmateaid.com/ask-the-inmate/How-long-will-someone-get-locked-up-for-a-parole#answer
Accepted Answer Date Created: October 14,2015