The zero byte file is a little glitch (it is not used for anything)
The additional files should however be useful sculptie maps. If you open them they should look like waves of colour.
However - please note that sculpties can only be made from regular lathe, line and loft objects. If you use merge, mirror or booleans the smooth surface is broken for sculptie export. There are
ways around this limitation... but it pays off to be careful.
Perhaps start with a sculptie lathe, and see if that works - otherwise please send me the cvy file and exported BMPs and I will investigate.