10,000ft does not include non-working days (Official Holidays or weekends) in availability calculations. These non-working days are visualized on the Schedule as light gray vertical bands to let you see how project timelines overlap with weekends or holidays.
By default, the length of a work week in 10,000ft is five days, and the work week begins on Monday, making Saturday and Sunday non-working days. If needed, you can change these settings within Account Settings. Your team may work a 4 day work week with team members being unavailable Friday - Sunday; or you may have various team members working every day of the week. In these instances, you would want to adjust the length of the work week according to your scenario.
In another scenario, some companies consider Friday and Saturday to be weekend or non-working days. In these instances, the start of work week should be set to Sunday.