Specifying 4 makes Hudson schedule your builds to only run on a slave with 4 or more executors, and if your build is then run on a slave with 5 executors, the ...

... cloud-based iOS Simulators & Android Emulators ... slave-plugin":{"buildDate":"Jan 17, 2016 ... TeamForge<\/a>.","gav":"org.jenkins-ci.plugins:collabnet:1.1 ...