Create a new pipeline job called linktest:

pipeline {
    agent { label 'master' }
    stages {
        stage('build') {
            steps {
                echo "Hello World!"
            }
        }
    }
}

Execute the job. The resulting symlinks for lastCompletedBuild, lastSuccessfulBuild and lastStableBuild are all linked to '-1'. Execute the job again and the links will now point to '1'. The resulting links for build which are successful or stable are always 1 less than the actual good build number. The permalinks file is reporting correct build numbers.