Multi-site configuration option for sub-site

Hi guys

This site digitalscot.net has just been configured for multi-site. What I have been used to is that when you start a new sub-site, it is set up as site.com/sub-site

For some reason it is now wanting to set it up as sub-site.site.com

I didn't set it up my sysadmin did, so have they configured it this way, or is it a setting I can change? I want to revert to the previous format.

thanks, Neil.