It really depends on what you're trying to accomplish. If you want to maintain a focus on reducing drug use in prisons, then you would expect to see some integration and coordination of interdiction surveillance, treatment succession, and testing, and you'd want to keep that at a fairly high tempo.
If you want to rigorously enforce conditions imposed by the parole board on abstinence, for example, then you would expect to see a fairly high tempo of tests in the community.
In either case, the statistics can lead you down a rabbit hole. The real questions are how that drug use is related to the success or failure of offenders once they are released into the community, and what the behaviour of individual parole officers is in reporting relapses, for example, or breaches of the condition back to the board, and what the parole board's behaviour is in terms of considering whether or not that should lead to revocation or suspension of the conditional release.
The number regarding the frequency of random testing in either setting is only one very small piece of the equation. You need a lot of other information to really understand how that's assisting or not assisting the reintegration or rehabilitation efforts.