Error:Restoring Site backup

HI All,

         I am restoring the SP 2010 site in one the SP 2010 web application which is having only 1 site.When I try to restore it is showing me error as Database as reached max number of sites .I have tried commands as below

   Restore-SPSite -identity http://sp2010/sites/dempsp2010 -Path C:\sample.bak -Force