What does "unsupervised weekends" mean?

Our girls have unsupervised weekend visits with their grandmother. We meet up Friday afternoons in a public location for the hand off, and she brings them back on Sunday afternoons. The time and place was decided by us and grandma. We have occasionally changed it to earlier or later because of weather or appointments. And they have stayed for a 3 day weekend on holiday occasions. We just told their worker and it was fine.So yeah, it's more like a joint custody w. grandma. This has been their arrangement for as long as they have been in care, even before they came to us.They are supposed to get unsupervised weekends with their mom, but I don't know if that is going to happen. When it looked possible, the SW said it would basically be the same gig - Fri-Sunday and workout the drop off and pick up with their mom. We have a functional relationship with her, and I know they'll love staying with her but I am not looking forward to that, their mother is not the most punctual.