We namespace all deployments under "deployment.". So like if you have a deployment named "security.jar". The module name is "deployment.security.jar". If it's a nested deployment you just add the sub deployment as a suffix. my.ear/stuff.jar is "deployment.my.ear.stuff.jar".
Note that the configuration is slightly misleading in that it appears you can specify a module per login-module. Unfortunately due to a JAAS limitation, all modules in the stack have to have the same module= value. We will look into hacking that to allow each stack to have its own entry in a future release.