I'm very sorry, that was a mistake on my part when I entered the Serpent's sample content for the web page. Obviously I copied the content from another instrument and forgot to delete what wasn't there, including not only the cres-dim but also trills and fast repetitions ... The instrument manuals normally contain the right information, so in case of doubt one should trust them rather than our website.
The mistake has been corrected, it now displays the proper content of the serpent.
Btw, there's nothing wrong with your English!
Kind regards, David