Usually you would have it 1.2.3
3 is usually a relatively small fix so e.g. missing a " or something like that something relative minor except needed for it to work.
2 is usually a bigger bug fix, so lots of bugs fixed, and in some cases you may have a few small additions.
1 is usually massive changes into core, many bug fixes, and lots of additions.
Very few will have it 1.2.3.4
