Baan 4 c3

We are playing with desktop manipulation for our system guys. They don't like the baan standard desktop manager, tttdskprogman. I created a copy session that copies one desktop to another, but am having just a little problem with ttdsk230, ttdsk240, and ttdsk250.
I understand where you get the next free number for a desktop, ttdsk201, but where do they get the phid's for ttdsk230.phid, ttdsk240.phid, and ttdsk250.phid? Are these free numbers set up somewhere else?

We're in no hurry--it's something I'm playing with, but would like to learn just a little more.....
thanks in advance.

I'm not sure but I don't think it's a first free number. I think the other two tables get the number from ttdsk250.