PxNUy in DLOAD subroutine!


I have modeled a panel cross-section with plane strain elements with reduced integration (CPE4R).
I am applying pressure load on one of the edges of the panel. The load has both spatial as well as temporal variation. Basically, a spatially non-uniform load moves back and forth as time advances. I have written a DLOAD subroutine for this in ABAQUS.
For such loads:
Load label in ABAQUS under *DSLOAD keyword is “PNU”
Load label in CalculiX under *DLOAD keyword is “PxNUy”

Can someone please explain what exactly are x and y here and how to enter them?

The following excerpt is from ccx_2.19 doc. It is not helping. (*DLOAD):
“… For nonuniform pressure, the label takes the form PxNUy, and the user subroutine dload.f must be provided. The label can be up to 20 characters long. In particular, y can be used to distinguish different nonuniform loading patterns (maximum 16 characters)…”


x is the number of the face, as explained a bit earlier in the User’s Guide:

The surface loading is entered as a uniform pressure with distributed load type label Px where x is the number of the face.

y can be defined by the user and it serves the role of distinguishing between different nonuniform loads defined in dload.f subroutine, if I understand it correctly.