Hi i’m just touch the Mikrotik but for my router when I try to allow the one PC go to Internet it will pop-up in log info like attach Picture and one can tell me why it can nat my Public to other IP that I concern it spam or what ,How can i stop it , Thank for help 
Hello,
most people posting here need some kind of help,
so first of all and since it seems that English is not your mother tongue:
Short sentences and descriptive information about your problem please 
Also a dump of your config might help, generate it in terminal with command
/export hide-sensitive
and post it.
greets
Thank