Re： about the setting of CST MWS PML

Dear, all
(1) In the setting of PML - 'open(add space)', there is a 'automatic minimum distance to structure', the default value of this setting is '5'. That means 5-meshline sapce is added to surround the structure.
(2) I also notice that in the setting of 'Background Properties', there are also some settings for 'surrounding space', including lower and upper x,y,z distance.
So what's the difference between the above two added space, inter-related or act separately? pls offer me some hints, tks a lot.
PS:
BTW, any idea about what kind of PML is used in CST?

ok, for the problem of add space in PML setting, I have solved. thanks for all of your attention.
my second question, "what kind of PML is used in CST", remains unsolved, if anybobdy has any ideas, kindly let me know. tks in advance.