nmap can scan a single host, a list of hosts or a subnet range. The lab network is 10.0.0.0/24, which means the only ip addresses on the lab network are 10.0.0.1 through 10.0.0.254. If you ask nmap to scan other ip-address it will, and it might take a long time since those ip-addresses won't reply. Limit your scanning to the 10.0.0.0/24 subnet range. The /24 is synonymous with a subnet mask of 255.255.255.0, and means treat the first 24 bits as a network address and the last 8 bits as the host address. That essentially means, 10.0.0.0/24 refers to all the addresses between 10.0.0.0 and 10.0.0.255.

Start by scanning your own servers, including scanning the Kali VM you are using nmap from.

Experiment with some different port scans.