Why is my C++ certification at 97%

I did the C++ certification test and it says I got 97% certification score. I am wondering why this is not 100%, as I did all the problems. Is this due to the amount of time I spent, or did my code fail a system test or something?

You may have failed a validator. They act as hidden testcases to score your solution, it’s to prevent hardcoding

Some tests/validators are not good enough, it can happen that you pass all tests but not all validators. This inconvenience is quite rare.