How to add range of ip's in outbound rules->Security Group

I'm not 100% sure what is meant by "range of IPs".

You can use subnet masks to specify a network range. For example, you could specify 172.16.0.0 with a mask of 255.255.240.0 which covers 172.16.0.0 - 172.16.15.255`.

You can also create prefix lists which are groups of IP addresses that you can then assign to security groups.

To add to what my colleague said, here is some more info how Subnet CIDR blocks work

The CIDR block of a subnet can be the same as the CIDR block for the VPC (for a single subnet in the VPC), or a subset of the CIDR block for the VPC (to create multiple subnets in the VPC). The allowed block size is between a /28 netmask and /16 netmask. If you create more than one subnet in a VPC, the CIDR blocks of the subnets cannot overlap.

For example, if you create a VPC with CIDR block 10.0.0.0/24, it supports 256 IP addresses. You can break this CIDR block into two subnets, each supporting 128 IP addresses. One subnet uses CIDR block 10.0.0.0/25 (for addresses 10.0.0.0 - 10.0.0.127) and the other uses CIDR block 10.0.0.128/25 (for addresses 10.0.0.128 - 10.0.0.255).