Set downtime to block apps during the day (not at night)

The standard setting for Downtime on my system is from 22:00 to 7:00, that is, from ten in the evening to seven in the morning, or over night. Instead of blocking apps over night, I want to block them *during the day*, specifically from 8:00 to 12:00 in the morning. But when I enter those times in Downtime, the apps are blocked all the time. Here is a screenshot that shows that when I set a block for 8:00 to 12:00 on Fridays, apps are blocked at 23:37 on a Friday: So how do I set a downtime during the day, not over night?