To get the range you want you'd need to calculate the CIDR.
There are some good online tools for doing this.
If you go to:
Input 18.104.22.168 as the IP address then select 14 as maximum address (lowest number that will accomodate the 10 you want) it will show you:
NETMASK should be 255.255.255.240.
First IP is actually 22.214.171.124 and last IP is 126.96.36.199. This encompasses the range you specified (188.8.131.52 - 184.108.40.206). It also gives you the CIDR (/28).