I don’t claim to be an authority on explaining the words of a godol, but it seems pretty simple.
1. Yungerman – A man who sees the girls in the class as being the same age or a bit younger than girls he went out with is too young. A man who sees the girls in the class as being the same age as his daughters is safer.
2. Yiras shamayim needs no explanation.
3. He needs to understand what the issues are. Not just that there are issues but what they are. Otherwise, lines can be crossed with no ill intent.