Means very little in my experience.

Even first thing in the AM, say 8 AM, it doesn't mean "hey I might be sleeping late, please keep it down". I've had the ladies whooping it up right outside my door shouting their weekend plans to each other after being up most of the night with a sick child.

I've also had them barge in a few minutes after checkout time (say 11 AM) although I've been granted a late checkout.

Occasionally, I've gone to workout either early in the morning or even mid-day if work was close to allow a lunch time jog. As my luck goes, these will be the times they choose to clean my room, so I've been leaving the DND sign out at these times. But it can backfire too if they never come back or I forget to remove it in my rush out the door...