Overstay information

Hello. I overstayed my visa by 6 days. The custom officer showed me the date on my passport by which I should have left the country, but he let me out without any fine. In my passport there is no mark or stamp that says that I overstayed. My question is: does this 6 days overstay is saved somewhere in their system, and can it interfere with my next visa application? Again - he didn't put any "warning stamp" in my passport.