No way, I (we) do not get contact with skin sellers skin creators in general. I do not intend to buy all skins just to explane to someone how it is done (as fas as I myself understand how)
I create skins for my own, sometimes on an existing basic skin, so for the items of my interest I do TEST all functions and behaviour of the parameters, taking good care to keep the original, and only make changes on a copy, so I can always go back to a working one.(you find the change after switch from big skin to minimized skin, and back .Then you see the change( that must be saved of course), so no restart of the radio is needed
Big chance that person selling skins even was not a member of the forum, but he might be as well, since the database and the whole site had a few crashes in the far past, and after the first big crash, members had to sign-up new for the whole accountsbase was lost.( That was jan-01-2010, see member admin signed in on that date after recreation of the whole site)
For now I, nor any other member (in my knowledge) had any contact with the new admin. ( with contact I mean, even no response on mails from our site to admin or the Bestware-board adress) so I even do not know admin speaks/understands english. And to be clear: I have not any connection with the RadioSure system. Only the former admin
asked me to keep an eye on the board
and keep it clean from advertisers (especially for porn sites and some freaks publishing whole books, or reports about sports-events , in the idea RadioSure is a radiostation where they could advertise for free)
Since the last crash and new arising of the sites, I appeared I had still my MOD-rights, so I am going on with taking care of the forum as much as I can,
altough all members can contribute by responding to questions
So my advice, since you have the skin: make a copy of it for safe, and work on a copy and test all items, how they look an how they behave, and you'll be an expert after that

OR you can wait till some other owner of that specific skin can help you out.
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edit: after looking
at the picture of the skin , My idea is that not the slider is changed, but the effect is just by selection of background / foreground colors for text , Normal/or Bold selection, since the element is LIST, and in all skins I know, there are no parameters between the start of the element and the end of it. In the xml file of Radiosure , there is no line about the listing, and in my knowledge, the list box ( a multiple- choice-field in terms of databases and spreadsheet) is defined in Windows ( and can vary with the windows version), and the slider is alwaays right if the box contains more items than the visible area, otherwise no slider is shown. Maybe you can look if the skin goes along with a special .dll file you have to install, If NOT then it must be just a visual effect of color choices in the list field and maaybe the baackground color of the skin image itself