I can't pull up the article, but for a while only the father could count anything- time, bible study or RV with minor children. They also limited it to 4 hrs. per month, no matter how much time you actually spent. The only way a lady could count the time and study was if she was "the spiritual head of the house" due to unbelieving mate or single mom.
Used to make me mad> another way they favored men.