How long did it take to see improvements in rehab?

Hi everyone. My dad recently had a stroke and has been in inpatient rehab for two weeks. He gets 15 hours of therapy a week but doesn’t seem to be making a lot of progress. I know it’s a long process but I thought we’d see some improvements by now. I’m worried because insurance only approved him for 3 weeks. The doctor is going to push for an extension but it’s not guaranteed. I’m curious how long it took for you or your loved one to really see progress during rehab? My dad can’t use his entire right side.