It’s in the article: It wasn’t until she was 17 years old — roughly three years after the visit from DSS — that the woman claims Koskan penetrated her with fingers for the first time at his home in Wood, South Dakota. The woman said that touching led to sexual intercourse, which took place “many times” in different residences across the state.
Hmmm first line at the link provided says 14-19yrs old.