You're right that it indicates a range of addresses, the number after the slash is the number of starting bits that the addresses all share.

Check out CIDR Blocks for a more complete answer: https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing...

/8 is the same as a 255.0.0.0 subnet mask. Also known as a class A subnet. In other words, literally any IP address that starts with “3.” In other other words, 16,777,216 IP addresses. In other other other words, about half a percent of the total number of public IPv4 addresses. Crazy.

Yep. https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing... for more info.