Corrections also is subtracting 169 days from Powell's sentence because his offense was nonviolent, Davis explained.
That leaves Powell with 338 days to serve in prison.
Powell is at a prison in Shelton, Wash., where all new Department of Corrections inmates go to receive an evaluation before being transferred to another facility to serve the remainder of their term. Davis said there is a chance Powell will be shipped to a prison in another state.
Powell was a civilian employee of the Department of Corrections before his arrest in September, and the department may decide it is a conflict of interest to keep him in one of its prisons.
Powell is being held in administrative segregation due to the notoriety of his case, Davis said.
Also, Davis said Powell has been classified as "low risk" to commit another crime upon release.
Susan Powell was reported missing from her home in West Valley City on Dec. 7, 2009. Her husband, Josh Powell, was the only person of interest ever named by police.
He claimed he last saw his wife the night before as he left with their two sons, then ages 4 and 2, and went camping in the west desert during a snowstorm.
While investigating the disappearance, West Valley City police served a search warrant on Steve Powell's home in Puyallup, Wash., where they found the photographs of neighbor girls.
On Feb. 5 of this year, Josh Powell murdered his sons, Charlie and Braden, and killed himself in a fire at his rented home in Graham, Wash.
In May, a Pierce County, Wash., Superior Court jury found Steve Powell guilty of 14 felony counts of voyeurism. At the sentencing hearing two weeks ago, Judge Ronald Culpepper dismissed two counts, saying they appeared to be for multiple photographs taken in the same session.