SOLVED: I see that this case was described in the Help page:
Note:
Select box marked “Required”: Using a minus symbol – for the value (after |), will mark an option as invalid! Example:
Your age#Please pick your age group|-#12 to 18|kiddo#19 to 30|young#31 to 45#45+ |older.
“Please pick…” is shown but not considered a valid value.
GREAT! It works, Thanks!