Ha I find this funny as I can tell a lot of guys have a 'kiss code', whereas girls really don't.
I always chuck on at least 4 x's, no matter the person. Some guys I know use none, then maybe will add 1, then immediately feel embarrassed and go back to none ha. The guy I'm seeing used to give none when we were friends, upped it to 1 when he said he liked me, and matched my 4 now we've taken things a bit further...makes me giggle how much thought goes into it!
Seriously all my girl friends use varying amounts...never read into it!!