linux - How do I add storage with cloud templating?

I have a CloudFormation template to spin up an EC2 instance.

Parameters:
  InstanceType:
    Type: String
    Description: Instance type for RStudio. Default is t2.micro.
    AllowedValues:
      - t2.micro
      - t2.small

      - t2.medium
      - t2.large
    ConstraintDescription: 'Valid instance type in the t2 family'
    Default: t2.micro
  ImageId:
    Type: 'AWS::EC2::Image::Id'
    Description: >-
      Amazon Linux Image ID. Default is for 2017.03.01 (HVM). N.B. 
    Default: ami-4fffc834

When I spin up the instance manually, there is an option to add storage. It defaults to 8gb and I'd like to do 16gb instead.

I looked for the syntax to add storage with CloudFormation. What is the syntax to set a volume size other than the default?