By default, cvsnt will assign numeric revisions by leaving the first number the same and incrementing the second number. For example, 1.1, 1.2, 1.3, etc.
When adding a new file, the second number will always be one and the first number will equal the highest first number of any file in that directory. For example, the current directory contains files whose highest numbered revisions are 1.7, 3.1, and 4.12, then an added file will be given the numeric revision 4.1.
There is no reason to care about the revision numbers--it is easier to treat them as internal numbers that cvsnt maintains, and tags provide a better way to distinguish between things like release 1 versus release 2 of your product (the section called “Tags-Symbolic revisions”).