Hi, I'm Dutch and I've been on the site also. Now I haven't gone to Holland Casino (since I'm just 16

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And I think what they mean by a "round" is (when playing a 6-Deck) when all the cards in the deck have been dealt. Or the card have been dealt down to 15 or whatever.
I'm not sure of this but at least that's what I got from their site.
You can aslways ask addtional info though.
Hope this helps a bit.
P.S: If you're gonna go to Holland to play in a Casino. please let me know because I'm very interested what gambling in a Dutch casino's like.