Flexible hours - what does yours actually look like?

Just negotiated "flexible hours" with my new employer. Want to get a real sense of what that means in practice at other companies before I get surprised:

• Can I really start at 10am if I finish at 6pm?
• If I work Saturday am do I get time off Wed afternoon?
• Is it actually flexible or just "flexible if nothing goes wrong"?

Sharing what I agreed to: 8am-4:30pm core hours, flex before/after, no expected weekend work, can take 1.5-2 hour lunch for school pickups if I make time up same day.

What's reasonable to expect?