When my DD was being homeschooled, "how many hours" wasn't a question that was asked. DW decided what subjects she wanted to cover on which days, and then provided materials and discussion to DD based on that. However long DD took to understand and practice, that was how long it took. Once DD demonstrated she was ready to move on, they moved on. More time might be used if DD asked for more.
The homeschool day typically lasted 3 hours. Because it was all at the appropriate pace and level of DD, those 3 hours were far more productive than the 7 hours she spends at a B&M school.
