[Integrity] How do I checkout a sub-project in a top level project?

I have question about Integrity API connection (API Version: 4.12.4301), I am using Jenkins CI server to poll PTC Integrity’s source code repository, there is a Jenkins plugin can help me to access my Integrity top level project, but if I want to check-out a sub-project of the top level project, the API will give me the MKS125212 error message, like below log.

Preparing to execute si projectinfo for #/168/DAP2500AB A/

An API Exception was caught!

The project #/168/DAP2500AB A/ could not be located on the server 172.16.0.19:7001: MKS125212: The project file /168/DAP2500AB A/project.pj is not registered as a top level project with the current server.

si projectinfo --user=tw.168.sw.01 --port=7001 --hostname=172.16.0.19 --project=#/168/DAP2500AB A/ -- returned exit code 128

Finished: FAILURE

How do I checkout the project in “#/168/DAP2500AB A”, not all projects in “#/168”?

Thank you,

Snaku