What is tpos

Fred

I am working on the example 7.1 fluid flow in mixer. While I have to write a file named cgrid.cgrd

but it's really bordering me and i can't find any hint about the content, for example:

*SET TANG TIME * DPS ! to calculate the tan value

*GET TPOS Y 37 !in this sentence,what does "tpos" mean?

*SET TOFF TANG - TPOS !and what does this whole sentence mean?

Thank you guys a lot!

Star-CD is really hard for me to study...Jesus!