AWS Instance Type size defaulting to a specific size during EC2 Launch programatically

Hi All, I am trying to do the following. I am using the AWS SDK and trying to launch an EC2 VM with an instance size of 100GB. I can see the request header containing the size I chose, but while provisioning this it is returning a different size. I dont have access to the AWS console. Can someone let me know what service or policies can default the size of an AWS Ec2 VM before launching ? I am using the AWS SDK and the RunInstancesRequest and withInstanceType(InstanceType instanceType) method. Same behaviour across all locations.