The scans have settings to manage how many hosts and NVTs can be run concurrently, so you can configure your GVM server to manage a large target. The default upper limit is 4095 hosts. You can read why here. So, the max hosts number is quite high.
If you are talking about the reports for a large number of hosts, then you can use a filter to filter the scan task results and then create a filtered report say per IP or groups of IPs.
I suggest starting with a solid review of the manual and scanning a host section.
If you have another question, please create a new thread for it. Thanks.