does this count only apply to post deleted by mods only ?
Do you mean the count on
BPIP? If so: yes. It counts deleted posts mentioned in
modlog, which only shows the results of Moderator actions.
If we delete the post ourself or it is deleted by Self-moderated OP or the whole thread is trashed by the mods, then in these cases how do we look at them when considering good or bad posting ?
We don't

In general, we judge users by the posts that aren't deleted. If you learn from your mistakes, and check the
forum rules to see which ones you've broken, a few deleted posts shouldn't be much of a problem.